Electrochemical reduction of metal salts as a method of preparing highly dispersed metal colloids and substrate fixed metal clusters by electrochemical reduction of metal salts

ABSTRACT

The object of the invention is a method for the electrochemical preparation of metal colloids with particle sizes of less than 30 nm, characterized in that one or more salts of one or more metals of groups Ib, IIb, III, IV, V, VI, VIIb, VIII, lanthanoides, and/or actinoides of the periodic table are cathodically reduced in the presence of a stabilizer, optionally with a supporting electrolyte being added, in organic solvents or in solvent mixtures of organic solvents and/or water within a temperature range of between -78° C. and +120° C. to form metal colloidal solutions or redispersible metal colloid powders, optionally in the presence of inert substrates and/or soluble metal salts of the respective metals. The invention further relates to soluble or redispersible colloids as well as application on substrates and immobilization thereof, in particular for the preparation of catalysts.

The present invention pertains to an electrochemical method of preparingsoluble metal colloids and substrate fixed metal clusters. The inventionalso includes electrochemical preparation of soluble bimetallic colloidsand substrate fixed bimetallic clusters.

BACKGROUND OF THE INVENTION

As is well-known, soluble or substrate fixed finely distributed metals,metal colloids and metal clusters are valuable catalysts in organic andinorganic chemistry as well as in electrochemistry (fuel cells) [G.Schmid, Clusters and Colloids, VCH, Weinheim 1994; J. P. Fackler,Metal-Metal Bonds and Clusters in Chemistry and Catalysis, Plenum Press,New York 1990; B. C. Gates, L. Guczi, H. Kn ozinger, Metal Clusters inCatalysis, Elsevier, Amsterdam, 1986; S. C. Davis, K. J. Klabunde, Chem.Rev. 82 (1982) 153]. This involves the reduction of metal salts byreducing agents, such as hydrogen, alcohol, formaldehyde, hydrazine,alkali metals, anthracene activated magnesium, or boron hydrides. Thesynthesis often employs stabilizers which prevent undesired formation ofmetal powders. These include ligands (e.g. phenanthroline derivatives),polymers (e.g. polyvinylpyrrolidone), and surface-active agents (e.g.tetra-alkylammonium salts) [see for instance: G. Schmid, B. Morun, J.-O.Malm, Angew. Chem. 101 (1989) 772; Angew. Chem., Int. Ed. Engl. 28(1989) 778; M. N. Vargaftik, V. P. Zagorodnikov, I. P. Stolarov, I. I.Moiseev, J. Mol. Catal. 53 (1989) 315; J. S. Bradley, J. M. Milar, E. W.Hill, J. Am. Chem. Soc. 113 (1991) 4016; F. Porta, F. Ragaini, S.Cenini, G. Scari, Gazz. Chim. Ital. 122 (1992) 361; H. B onnemann, W.Brijoux, R. Brinkmann, E. Dinjus, T. Joussen, B. Korall, Angew. Chem.103 (1991) 1344; Angew. Chem., Int. Ed. Engl. 30 (1991) 1312; M.Boutonnet, J. Kizling, P. Stenius, G. Maire, Colloids Surf. 5 (1982)209; M. Boutonnet, J. Kizling, R. Touroude, G. Maire, P. Stenius, Appl.Catal. 20 (1986) 163; N. Toshima, T. Takashashi, H. Hirai, Chem. Lett.1985 1245; K. Meguro, M. Toriyuka, K. Esumi, Bull. Chem. Soc. Jpn. 61(1988) 341; N. Toshima, T. Takashashi, Bull. Chem. Soc. Jpn. 65 (1992)400; J. Blum, Y. Sasson, A. Zoran, J. Mol. Catal. 11 (1981) 293; N.Satoh, K. Kimura, Bull. Chem. Soc. Jpn. 62 (1989) 1758]. Sometimes metalvaporization is used [G. Schmid, Clusters and Colloids, VCH, Weinheim1994; J. P. Fackler, Metal-Metal Bonds and Clusters in Chemistry andCatalysis, Plenum Press, New York 1990; B. C. Gates, L. Guczi, H. Knozinger, Metal Clusters in Catalysis, Elsevier, Amsterdam, 1986; S. C.Davis, K. J. Klabunde, Chem. Rev. 82 (1982) 153]. Drawbacks of thesemethods are, inter alia, (1) the high costs of metal vaporization and ofsome reducing agents; (2) partial or undesired formation of metalpowders; (3) tedious separation procedures for the purification of themetal clusters or colloids; (4) contamination by partial incorporationof reducing agents (e.g. hydrogen or boron); (5) lack or limitation offacilities for controlling the particle size. Specific and simplecontrol of particle size while synthesis and isolation are simple wouldjust be a large progress, however, all the more, since the catalyticproperties of metal colloids and metal clusters depend on particle size[A. Duteil, R. Queau, B. Chaudret, R. Mazel, C. Roucau, J. S. Bradley,Chem. Mater. 5 (1993) 341].

Drawbacks of the above mentioned methods are, inter alia, the high costsof some reducing agents; tedious separation of by-products; impureproducts from undesired partial incorporation of reducing agents (e.g.hydrogen or boron); and/or lack or limitation of facilities forcontrolling the particle size.

It is known that in conventional metal powder production,electrochemical processes are also used wherein use is made either ofanodic dissolution with subsequent reduction at the cathode or ofreduction at the cathode of metal salts employed [N. Ibl, Chem.Ing.-Techn. 36 (1964) 601]. These methods are inexpensive and oftenclean with respect of the formation of by-products (R. Walker, A. R. B.Sanford, Chem. Ind. 1979, 642; R. Walter, Chem. Ind. 1980, 260). Thisinvolves the use of aqueous electrolytes which in most cases comprisesulfuric acid. Although metals and alloys of different morphologies canbe prepared in this way, one drawback is the concomitant formation ofmetal hydrides through H₂ formation at the cathode which is frequentlyobserved [N. Ibl, G. Gut, M. Weber, Electrochim. Acta 18 (1973) 307].The major drawback, however, is the fact that to date the preparation ofsoluble nanostructured colloids in the range of up to 30 nm has not beenaccomplished. Rather, deposition of metal powder in the form of largecrystallites in the nm or μm range occurs as a rule.

SUMMARY OF THE INVENTION

The inventors of the present application have now developed a novelelectrochemical process for the preparation of nanostructured metalclusters or colloids in a first embodiment, according to which an anodeconsisting of a metal sheet serves as the metal source [M. T. Reetz, W.Helbig, J. Am. Chem. Soc. 116 (1994) 7401]. Surprisingly, it has nowbeen found that electrochemical synthesis of soluble metal colloids canbe achieved by operating in an inert organic, aprotic solvent, withsurface-active colloid stabilizers being added as the supportingelectrolyte which on one hand will prevent plating of the metal and onthe other hand will protect or stabilize the rather Small metal nucleiin the cluster stage. A metal sheet serves as the anode to be dissolvedand a metal or glassy carbon electrode serves as the cathode (scheme 1).After dissolution at the anode, the released metal salts are reducedagain at the cathode, with tetraalkylammonium salts serving asstabilizers (scheme 1). Organic solvents are employed. ##STR1##

As the supporting electrolyte and at the same time as a stabilizer forthe colloids, quarternary ammonium or phosphonium salts R¹ R² R³ R⁴ N⁺X⁻ and R¹ R² R³ R⁴ P⁺ X⁻, respectively, are suitable. A wide variety ofcombinations of R¹, R², R³ and R⁴ are possible Examples include thesymmetrical tetraalkylammonium salts with R¹ =R² =R³ =R⁴ =n-butyl orn-octyl, the mixed tetraalkylammonium salts with R¹ =R² =R³ =methyl andR⁴ =cetyl, or chiral tetraalkylammonium salts having four differentresidues. Aryltrialkylammonium salts may also be used. Suitable counterions include various anions, e.g. halogenides (Cl⁻, Br⁻, I⁻),hexafluorophosphate (PF₆ ⁻), carboxylates R'CO₂ ⁻ (R'=alkyl, aryl), orsulfonates R"SO₃ ⁻ (R"=alkyl, aryl). A similar variety of phosphoniumsalts may be used, including tetraarylphosphonium salts, such astetraphenylphosphonium bromide. Preferably, tetrabutylammonium chloride,bromide or hexafluorophosphate, tetraoctylammonium bromide, ortributylhexadecylphosphonium bromide are employed. As the metals, inparticular transition metals, for example Fe, Co, Ni, Pd, Pt, Ir, Rh,Cu, Ag, or Au, are used. Suitable solvents are aprotic organic solvents,such as tetrahydrofuran (THF), toluene, acetonitrile (ACN), or mixturesthereof. The temperature in the electrolytic cell may be in the rangebetween -78° C. and +120° C., preferably 15°-30° C. or room temperature.

In this way, metal colloids of various metals and metal alloys havingvarious sizes and being stabilized by quarternary ammonium orphosphonium salts can be synthesized. The size of the metal colloids isdetermined by varying the current density which immediately affects thereduction potential of the cathode. The higher the overvoltage, which isdefined as the deviation of the reduction potential from the equilibriumpotential, the smaller becomes the maximum size of the metal nuclei inthe electrolytic boundary layer. These nuclei are trapped which isachieved by the fact that the surface-active agents used as supportingelectrolytes form a protective shell around them and thus preventfurther growth. Thus, the size of the metal colloids can be controlled.For instance, soluble Pd colloids stabilized by tetraoctylammoniumbromide can be prepared with selected diameters of about 2 nm, 5 nm, or10 nm, depending on the current density applied, i.e. 3.4, 1 and 0.4mA/cm², respectively, at the same concentration of the stabilizer.

This method has the advantage that the R₄ N⁺ X⁻ stabilized metalcolloids are formed without notable by-products and hence are readilyisolated, that controlling of the particle size by adjusting the currentdensity and/or the overpotential is possible, and that immobilization ofthe colloids by fixing them on substrates can easily be performed. Somemetal sheets are more expensive than the respective metal salts; somemetal sheets, especially in the case of metals very resistent tooxidation, cannot be dissolved at all anodically or only poorly so. Fromthe redox potentials of the metals which can be found in tables in therelevant literature [Handbook of Chemistry and Physics, CRC Press, BocaRaton, Fla. (U.S.A.), 1988], the latter behaviour can be understood.Metals such as for instance Pt or Rh can be anodically dissolved onlyconditionally in the described medium according to scheme 1. However,dissolution is a precondition for the above embodiment to succeed.

Another embodiment of an electrochemical method has now been foundaccording to which metal salts are used and are reduced at the cathodeto form stabilized clusters in the nanometer range. The invention willbe successful even if metal salts are used whose corresponding metalsheet is readily dissolved anodically.

For performing the metal colloid synthesis of the invention according tosaid further embodiment, metal salts MX_(n) are used for electrochemicalreduction, where quite different ligands X are suitable. In addition tohalogenides (F, Cl, Br, I), mention may be made, in particular, ofcarboxylates RCO₂ ⁻ (e.g. R=CH₃, CF₃, C₂ H₅, C₃ H₇, C₄ H₉, C₆ H₅) fromsimple carboxylic acids, from fatty acids (e.g. R=C₁₇ H₃₅), and fromchiral carboxylic acids [e.g. R=CH(CH₃)C₆ H₅ ], of sulfonates RSO₃ ⁻(e.g. R=CH₃, CF₃, CH₃ C₆ H₄), and of acetylacetonates. The metals in thesalts MX_(n) may be main group elements, for instance Ga, In or Tl, aswell as transition metals, for instance Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd,Ag, Os, Pt, or Au. The above-mentioned ammonium or phosphonium saltsserve as stabilizers for the colloids.

The above-mentioned organic solvents, such as for instancetetrahydrofuran (THF), toluene, propylene carbonate, acetonitrile (ACN),or mixtures thereof as well as mixtures of THF and H₂ O or of ACN and H₂O, serve as solvents. Mixtures of THF and alcohols, such as methanol orethanol, or of ACN and alcohols may also be used. The temperature in theelectrolytic cell may be within the above-mentioned range. As the anodeand the cathode, inert electrode materials conventionally used inelectrochemistry, e.g. Pt sheets or graphite, are selected.

Whereas the metal clusters with the above-mentioned stabilizing ammoniumor phosphonium salts are soluble in organic solvents, water solubilityis achieved by using ionic (cationic, anionic, zwitterionic) ornon-ionic stabilizers which are readily soluble in water, optionally inthe presence of a supporting electrolyte, such as e.g. lithium chloride,lithium acetate, or tetramethylammonium acetate. As cationicstabilizers, e.g. fully or partially esterifiedmethyltri(hydroxyethyl)ammonium or -phosphonium salts as well ascompounds of the type R¹ R² R³ R⁴ N⁺ X⁻ or R¹ R² R³ R⁴ P⁺ X⁻, with e.g.R¹ =(CH₂ CH(OH)CH₂ Cl ), R²⁻⁴ =alkyl or aryl, are used. The anionicstabilizers include e.g. alkali metal salts of amino acid derivatives,such as e.g. sodium alkylamido-N-hydroxyethylglycinates or succinates.Suitable zwitterionic stabilizers include e.g. (CH₃)₂ N⁺ (C₁₂ H₂₅)CH₂CH₂ CH₂ SO₃ ⁻, (CH₃)₂ N⁺ (C₁₂ H₂₅)(CH₂)_(x) CO₂ ⁻ (x=1-3), orcocamidopropyl betaines. The group of the non-ionic stabilizers includese.g. sugar derivatives, such as the commercially available substances ofthe TWEEN® group, modified cyclodextrines, polyglycosides,octanoyl-N-methylglucamide (MECA-8), heptylglucopyranoside, poly(vinylalcohol), and also polyoxyethylene alkyl ethers (BRIJ 35).

The present invention allows for the preparation of metal colloidsaccording to the second embodiment of various metals having differentsizes. The size of the metal colloids is determined by varying thecurrent density which immediately affects the reduction potential of thecathode. The higher the overvoltage, which is defined as the deviationof the reduction potential from the equilibrium potential, the smallerthe particle size.

For the preparation of bimetallic, trimetallic or multimetallic metalcolloids, mixtures of two or more different metal salts are employed.Another method of preparing metal alloys in the form of stabilizedcolloids consists in using as electrodes a readily dissolved metal anode(sheets of e.g. Al, Ti, Sn, Ni, Cu, Pd, Ag, or Au) and an inert cathode(e.g. a platinum sheet) with addition of a metal salt MX_(n) in a commonsolvent. The overall electrochemical process consists in that the anodeis oxidatively dissolved to form a second metal salt, and that bothmetal salts are concurrently reduced at the cathode to form bimetallicstabilized colloids.

To characterize the metal colloids, conventional analytical methods areused, in particular transmission electron microscopy (TEM) and elementalanalysis.

The embodiments according to the invention not only are inexpensive butalso have the following advantages:

1) simple isolation of the metal colloids.

2) virtually no by-products.

3) no incorporation of foreign substances, such as e.g. hydrides orboron.

4) availability of metal colloids and bimetallic or multimetalliccolloids that cannot be prepared by known electrochemical methods.

5) facility of simply controlling the particle size by adjustment ofcurrent density (or overpotential).

6) simple preparation of bimetallic colloids either by employing twodifferent metal salts or by using a dissolving metal anode incombination with an added metal salt.

7) simple variation of solubility of the metal colloids by selecting thestabilizer (solubility ranging from pentane to water).

8) preparation of halogen-free catalysts which are important forcatalysis.

The water soluble colloids prepared according to the invention can beused for the preparation of stable aqueous solutions with metal contentsof above 4 mmol of metal per liter. Also possible is the preparation ofaqueous solutions acidified with hydrochloric or sulfuric acid such asthose used in electroplating and electroforming technology, e.g. inelectroless plating [O. J. Murphy et al., "Electrochemistry intransition: From the 20 th to the 21st century", Plenum Press, New York,1992, page 39].

For the preparation of substrate fixed metal clusters, an undoped ordoped substrate or carrier (e.g. TiO₂) is covered with a solution in H₂O of a water soluble colloid, and the water is separated. An immobilizedmetal cluster is thus obtained in a simple manner. Alternatively, aslurry of the substrate in the electrolyte may be formed andelectrolysis performed in the presence of the substrate. The metalclusters generated are fixed in situ on the substrate (e.g. coal).Further substrates that may be used are active charcoal, metal oxides(for instance SiO₂, Al₂ O₃, MgO), or insoluble organic polymers (forexample a polyamide, such as Kevlar®). The substrate may be doted withone or more metals, said dotation being performed by classical methodsor by the electrochemical process described herein. The particle sizemay conveniently be determined by transmission electron micrographs. Ithas been found that the metal colloids according to the presentinvention can be coated in particular on the surface of inert substrateslike usual catalyst supports without penetration into the body of thesupport but providing in particular a monomolecular, bimolecular ormultimolecular layer of the colloid with good adherence properties tothe support surface.

The colloids prepared according to the invention can be used to applymetals in finely dispersed form on undoped or doped surfaces to formhighly active heterogeneous catalysts. On the other hand, the colloidsprepared according to the invention can be used as homogeneouscatalysts. The substrate fixed metal clusters prepared according to theinvention can be used as heterogeneous catalysts or as electrocatalystsin fuel cells. Thus, palladium colloids adsorbed on solid polymers orglasses serve as catalysts in electroless plating to metallizenonconductors. Another field of applications for the soluble colloidsand substrate fixed metal clusters prepared according to the inventioninvolves the development of novel materials having unusual electronicproperties and providing important stimuli in the development of novelsensitive electronic components and very high scale integrated storagemedia based on quantum point arrays.

The colloids on undoped or doped substrates prepared according to theinvention are highly active heterogeneous catalysts. They are usefule.g. as hydrogenation catalysts in hydrogenating olefins or aromatics.An application of technical interest is e.g. partial hydrogenation ofbenzene to form cyclohexene with substrate fixed ruthenium colloids orbimetallic colloids (e.g. Ru/Sn). The substrate fixed metal clustersprepared according to the invention may also be used as catalysts inHeck reactions, e.g. in the Pd-colloid catalyzed reaction ofbromobenzene and styrene to form stilbene. The heterogeneous catalystsare also useful as electrocatalysts in fuel cells (in particularsubstrate fixed Pt and Pt/Ru clusters). The metal colloids preparedaccording to the invention are useful as homogeneous catalysts, whichincludes their use in two-phase systems (for instance H₂ O/toluene),such as e.g. betaine stabilized Pd clusters soluble in H₂ O. The solublemetal clusters may also be embedded in polymers to prepare materials forelectronic, optical and magnetic applications. As the embeddingcomponent of those composite materials, there are used organic polymers,such as e.g. poly(p-phenylenevinylene), poly(methyl methacrylate),polysilanes, and polystyrene, or inorganic polymers, such as zeolites,silicates, and metal oxides. The sol-gel process which is well-known inthe art can be used to incorporate the metal clusters in amorphous metaloxide materials (e.g. SiO₂).

The soluble metal clusters can also be surface-deposited byelectrophoretics to prepare novel materials for applications in opticsand electronics, e.g. Pd on HOPG (highly oriented pyrolyric graphite).

To characterize the metal colloids, conventional analytical methods areused, in particular transmission electron microscopy (TEM) and elementalanalysis. Another method of investigation that may be performed involvescomparative studies by TEM/STM (scanning tunnel microscopy) which allowfor a precise characterization of the stabilizing protective shell. Thefollowing examples illustrate the new method in detail withoutrepresenting a limitation whatsoever thereof.

EXAMPLE 1

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF. Two sheets ofpure palladium (2×2.5 cm² geometric electrode surface area, thickness 1mm) at a distance of about 3 mm are used as the electrodes. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). With vigorous stirring by means of a magnetic stirrer, acurrent of 5 mA which is increased to 17 mA in the course of 20 minutesis passed between the palladium electrodes. By means of jacket cooling,the electrolytic cell is maintained at 16° C. In the course of theelectrolysis, the electrolyte turns deep-black. After a charge of 640 Chas been passed, the electrolysis is stopped and the electrolyte ispressed into a 150 ml nitrogenized vessel. During this period, 300 mg ofPd have dissolved anodically, corresponding to an anode efficiency of90% with an uptake by palladium of 2 electrons. Addition of 30 ml ofoxygen-free water to the electrolyte results in the formation of abrown-grey precipitate upon vigorous shaking. The latter is allowed toset for 24 hours whereupon the clear supernatant is syphoned off. Dryingunder oil pump vacuum for 20 minutes yields 411 mg (99% yield based onPd dissolved) of a grey-black powder which is amorphous by X-raydiffraction. This powder readily dissolves in THF, acetone, toluene,DMF, and is insoluble in water, diethyl ether, acetonitrile, andpentane. Elemental analysis: Pd: 72.80%; C: 19.13%; H: 3.27%; N: 0.60%;Br: 3.98%. Elemental analysis as well as the mass spectrum and NMRspectrum indicate the presence of Noct₄ Br which is a component of thecolloid powder and efficiently prevents agglomeration of the palladiumparticles which is also the case in the solid state, so the powderremains completely redispersible for months. Mass spectrum: m/z=353(trioctylamine).

Transmission electron micrographs show a narrow size distribution ofcolloids which are all ≦2 nm in diameter and have spherical geometries.Electrolyses in a mixed electrolyte of THF/pentane (1/1) orTHF/diethylether (1/1) proceed in much the same manner. Electrolysesperformed at -35° C. or in refluxing THF yield the same results, too.

EXAMPLE 2

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.05M tetraoctylammonium bromide in THF/ACN (4/1). Twosheets of pure palladium (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.All operations must be performed under an inert gas atmosphere (argon ornitrogen). Under ultrasonic action, a current of 5 mA which is increasedto 15 mA in the course of 20 minutes is passed between the palladiumelectrodes. By means of jacket cooling, the electrolytic cell ismaintained at 16° C. In the course of the electrolysis, the electrolyteturns deep-black. After 320 C have been passed, the electrolysis isstopped and the electrolyte is pressed under protective gas into a 150ml nitrogenized vessel. During this period, 155 mg of Pd have dissolvedanodically, corresponding to a current efficiency of 93% with an uptakeby palladium of 2 electrons. Addition of 20 ml of oxygen-free water tothe electrolyte results in the formation of a brown-grey precipitateupon vigorous shaking. The latter is allowed to set for 24 hourswhereupon the clear supernatant is syphoned off. After drying under oilpump vacuum for 20 minutes, 207 mg (99% yield based on Pd dissolved) ofa grey-black powder is obtained. This powder readily dissolves in THF,acetone, toluene, DMF, and is insoluble in water, diethyl ether,acetonitrile, and pentane.

Elemental analysis: Pd: 75.11%; C: 11.34%; H: 1.58%; N: 2.57%; Br:3.31%. Mass spectrum: m/z=353 (trioctylamine), 41 (ACN).

Transmission electron micrographs show a narrow size distribution ofcolloids which are all ≦2 nm in diameter and have spherical geometries.

EXAMPLE 3

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.05M tetraoctylammoniumbromide in THF/ACN (4/1). Twosheets of pure palladium (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.All operations must be performed under an inert gas atmosphere (argon ornitrogen). Under ultrasonic action, a current of 3mA which is increasedto 5mA in the course of 20 minutes is passed between the palladiumelectrodes. By means of jacket cooling, the electrolytic cell ismaintained at 16° C. In the course of the electrolysis, the electrolyteturns deep-black. After 320 C have been passed, the electrolysis isstopped and the electrolyte is pressed under protective gas into a 150ml nitrogenized vessel. During this period, 145 mg of Pd have dissolvedanodically, corresponding to a current efficiency of 88% with an uptakeby palladium of 2 electrons. Addition of 20 ml of oxygen-free water tothe electrolyte results in the formation of a brown-grey precipitateupon vigorous shaking. The latter is allowed to set for 24 hourswhereupon the clear supernatant is syphoned off. After drying under oilpump vacuum for 20 minutes, 180 mg (99% yield based on Pd dissolved) ofa grey-black powder is obtained. This powder readily dissolves in THF,acetone, toluene, DMF, and is insoluble in water, diethyl ether,acetonitrile, and pentane.

Elemental analysis: Pd: 74%

Mass spectrum: m/z=353 (trioctylamine), 41 (ACN)

Transmission electron micrographs show a narrow size distribution ofcolloids which are all ≦6 nm in diameter (maxima between 4-6 nm) andhave spherical geometries.

EXAMPLE 4

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.05M tetraoctylammoniumbromide in THF/ACN (4/1). Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure palladium (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 1 mA which isincreased to 2 mA in the course of 20 minutes is passed between thepalladium electrodes. By means of jacket cooling, the electrolytic cellis maintained at 16° C. In the course of the electrolysis, theelectrolyte turns deep-black. After 320 C have been passed, theelectrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 140 mg of Pd have dissolvedanodically, corresponding to a current efficiency of 85% with an uptakeby palladium of 2 electrons. Addition of 20 ml of oxygen-free water tothe electrolyte results in the formation of a brown-grey precipitateupon vigorous shaking. The latter is allowed to set for 24 hourswhereupon the clear supernatant is syphoned off. After drying under oilpump vacuum for 20 minutes, 175 mg (99% yield based on Pd dissolved) ofa grey-black powder is obtained. This powder readily dissolves in THF,acetone, toluene, DMF, and is insoluble in water, diethyl ether,acetonitrile, and pentane.

Elemental analysis: Pd: 74%

Mass spectrum: m/z=353 (trioctylamine), 41 (ACN)

Transmission electron micrographs show a broader size distribution ofcolloids which are all ≦12 nm in diameter and in addition to sphericallyshaped colloids also include cornered ones. The course of theexperiments in examples 1-4 will be absolutely analogous, if NMe₂dodecyl₂ Br or NMe₂ octyl₂ Br is used as the supporting electrolyte.

EXAMPLE 5

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.05M tetraoctylanunonium bromide in ACN. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure palladium (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 5 mA which isincreased to 20 mA in the course of 20 minutes is passed between thepalladium electrodes. By means of jacket cooling, the electrolytic cellis maintained at 16° C. In the course of the electrolysis, theelectrolyte turns deep-black. After 320 C have been passed, theelectrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 156 mg of Pd have dissolvedanodically, corresponding to a current efficiency of 95% with an uptakeby palladium of 2 electrons. The electrolyte is allowed to stand for 24hours during which a grey-brown to black precipitate is setting, and theclear supernatant is syphoned off. After drying under oil pump vacuumfor 20 minutes, 205 mg (99% yield based on Pd dissolved) of a grey-blackpowder is obtained. This powder readily dissolves in THF, acetone,toluene, DMF, and is insoluble in water, diethyl ether, acetonitrile,and pentane. Elemental analysis: Pd: 74%.

Mass spectrum: m/z=353 (trioctylamine), 41 (ACN)

Transmission electron micrographs show a narrow size distribution ofcolloids which are all ≦6 nm in diameter (maxima between 4-6 nm) andhave spherical geometries.

EXAMPLE 6

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.0125M tetraoctylammonium bromide in THF. Alloperations must be performed under an inert gas atmosphere. Two sheetsof pure palladium (2×2.5 cm² geometric electrode surface area, thickness1 mm) at a distance of about 3 mm are used as the electrodes. Underultrasonic action, a current of 2 mA which is increased to 9 mA in thecourse of 20 minutes is passed between the palladium electrodes. Bymeans of jacket cooling, the electrolytic cell is maintained at 16° C.In the course of the electrolysis, the electrolyte turns deep-black.After 160 C have been passed, the electrolysis is stopped and theelectrolyte is pressed into a 150 ml nitrogenized vessel. During thisperiod, 75 mg of Pd have dissolved anodically, corresponding to acurrent efficiency of 90% with an uptake by palladium of 2 electrons.Addition of 20 ml of oxygen-free water to the electrolyte results in theformation of a brown-grey precipitate upon vigorous shaking. The latteris allowed to set for 24 hours, whereupon the clear supernatant issyphoned off. After drying under oil pump vacuum for 20 minutes, 102 mg(99% yield based on Pd dissolved) of a grey-black powder is obtained.This powder readily dissolves in THF, acetone, toluene, DMF, and isinsoluble in water, diethyl ether, acetonitrile, and pentane.

Elemental analysis: Pd: 74%

Mass spectrum: m/z=353 (trioctylamine)

Transmission electron micrographs show a very broad size distribution ofcolloids which are in the range of 2-50 nm.

EXAMPLE 7

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in propylene carbonate.All operations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure palladium (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 5 mA which isincreased to 17 mA in the course of 20 minutes is passed between thepalladium electrodes. By means of jacket cooling, the electrolytic cellis maintained at 16° C. In the course of the electrolysis, theelectrolyte turns deep-black. After 640 C have been passed, theelectrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 283 mg of Pd have dissolvedanodically, corresponding to a current efficiency of 85% with an uptakeby palladium of 2 electrons. Addition of 30 ml of diethyl ether to theelectrolyte results in the formation of a brown-grey precipitate uponvigorous shaking. The latter is allowed to set for 24 hours, whereuponthe clear supernatant is syphoned off. The precipitate is then washedsuccessively with 5 ml of diethyl ether and 5 ml of pentane. Dryingunder high vacuum for 4 hours yields 346 mg (93% yield based on Pddissolved) of a grey-black powder. This powder readily dissolves in THF,acetone, toluene, DMF, and is insoluble in water, diethyl ether,acetonitrile, and pentane.

Elemental analysis: Pd: 76%

Transmission electron micrographs show a narrow size distribution ofcolloids which are all <6 nm in diameter and have spherical geometries.

EXAMPLE 8

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.03M tetrabutylammonium bromide in THF. All operationsmust be performed under an inert gas atmosphere (argon or nitrogen). Inthis solution, 3 g of 3-(dimethyldodecylammonio)propanesulfonate (9mmol) are suspended. Two sheets of pure palladium (2×2.5 cm² geometricelectrode surface area, thickness 1 mm) at a distance of about 3 mm areused as the electrodes. Under ultrasonic action, a current of 5 mA whichis increased to 13 mA in the course of 20 minutes is passed between thepalladium electrodes. By means of jacket cooling, the electrolytic cellis maintained at 28° C. During this period, the electrolyte turnsdeep-black. After 400 C have been passed, the electrolysis is stoppedand the electrolyte is pressed into a 150 ml nitrogenized vessel. Duringthis period, 190 mg of Pd have dissolved anodically, corresponding to acurrent efficiency of 92% with an uptake by palladium of 2 electrons.Within 24 h, a grey-black precipitate forms. The slightly red-coloredsupernatant is pressed off under protective gas and the precipitate iswashed twice with 10 ml of THF (thermostated at 30° C.). Drying underoil pump vacuum for 20 minutes yields 304 mg (88% yield based on Pddissolved) of a grey-black powder. This powder readily dissolves inwater and ethanol, and is insoluble in diethyl ether, acetonitrile, THF,DMF, and pentane.

Elemental analysis: Pd: 50%

Transmission electron micrographs show a narrow size distribution ofcolloids which are all <16 nm in diameter and have spherical geometries.

EXAMPLE 9

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetradodecylammonium bromide in THF. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure palladium (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. With vigorous stirring by means of a magnetic stirrer, acurrent of 5 mA which is increased to 12 mA in the course of 20 minutesis passed between the palladium electrodes. By means of jacket cooling,the electrolytic cell is maintained at 28° C. In the course of theelectrolysis, the electrolyte turns deep-black. After 640 C have beenpassed, the electrolysis is stopped and the electrolyte is pressed intoa 150 ml nitrogenized vessel. During this period, 275 mg of Pd havedissolved anodically, corresponding to a current efficiency of 83% withan uptake by palladium of 2 electrons. Addition of 10 ml of oxygen-freewater to the electrolyte results in the formation of a brown-greyprecipitate upon vigorous shaking. The latter is allowed to set for 24hours, whereupon the clear supernatant-is syphoned off. After dryingunder oil pump vacuum for 20 minutes, 375 mg (99% yield based on Pddissolved) of a grey-black powder is obtained. This powder readilydissolves in THF and toluene, and is insoluble in water, diethyl ether,acetonitrile, and pentane.

Elemental analysis: Pd: 72.58%; C: 9.87%; H: 2.02%; N: 0.75%; Br:11.12%. Mass spectrum: m/z=521 (tridodecylamine).

Transmission electron micrographs show a narrow size distribution ofcolloids which are all <4 nm in diameter and have spherical geometries.

EXAMPLE 10

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetrabutylammonium bromide in THF. All operationsmust be performed under an inert gas atmosphere (argon or nitrogen). Twosheets of pure palladium (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.With vigorous stirring by means of a magnetic stirrer, a current of 5 mAwhich is increased to 12 mA in the course of 20 minutes is passedbetween the palladium electrodes. By means of jacket cooling, theelectrolytic cell is maintained at 28° C. In the course of theelectrolysis, the electrolyte turns deep-black. After 640 C have beenpassed, the electrolysis is stopped and the electrolyte is pressed intoa 150 ml nitrogenized vessel. During this period, 308 mg of Pd havedissolved anodically, corresponding to a current efficiency of 93% withan uptake by palladium of 2 electrons. Addition of 10 ml of oxygen-freewater to the electrolyte results in the formation of a brown-greyprecipitate upon vigorous shaking. The latter is allowed to set for 24hours, whereupon the clear supernatant is syphoned off. After dryingunder oil pump vacuum for 20 minutes, 350 mg (99% yield based on Pddissolved) of a grey-black powder is obtained. This powder readilydissolves in DMF, and is insoluble in water, dyethyl ether, THF,acetonitrile, and pentane.

Elemental analysis: Pd: 86.46%; C: 8.98%; H: 1.68%; N: 0.76%; Br: 2.06%.Mass spectrum: m/z=242 (tetrabutylammonium); 185 (tributylamine).Transmission electron micrographs show a narrow size distribution ofcolloids which are all <4 nm in diameter and have spherical geometries.

Electrolyses using NBu₄ Cl, NBu₄ I, and PBu₄ Cl as stabilizers proceedin much the same manner.

EXAMPLE 11

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF. In thissolution, 2.8 g of thoroughly dried and mortar-ground active charcoal issuspended. All operations must be performed under an inert gasatmosphere (argon or nitrogen). Two sheets of pure palladium (2×2.5 cm²geometric electrode surface area, thickness 1 mm) at a distance of about3 mm are used as the electrodes. Under ultrasonic action, a current of 5mA which is increased to 15 mA in the course of 20 minutes is passedbetween the palladium electrodes. By means of jacket cooling, theelectrolytic cell is maintained at 16° C. In the course of theelectrolysis, the electrolyte turns deep-black. After 320 C have beenpassed, the electrolysis is stopped and the electrolyte is pressed intoa 150 ml nitrogenized vessel. During this period, 155 mg of Pd havedissolved anodically, corresponding to a current efficiency of 93% withan uptake by palladium of 2 electrons. Further processing includesaddition of 40 ml of ethanol and vigorous stirring. Filtering through aD4 frit and subsequent washing with 2 portions of 10 ml of ethanol anddrying under oil pump vacuum yields 2.9 g of a grey-black powder. Thecatalyst thus obtained comprises 5.5% of Pd. Transmission electronmicrographs show a narrow size distribution of Pd colloids in the rangeof 2 nm which are adsorbed on the active charcoal.

EXAMPLE 12

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF. Since the metalcolloid is very sensitive to air and moisture, special care is to betaken that the solvents are free of water and oxygen. All operationsmust be performed under an inert gas atmosphere (argon or nitrogen). Twosheets of pure nickel (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.Under ultrasonic action, a current of 5 mA which is increased to 15 mAin the course of 20 minutes is passed between the Ni electrodes. Bymeans of jacket cooling, the electrolytic cell is maintained at 16° C.In the course of the electrolysis, the electrolyte turns deep-black.After 320 C have been passed, the electrolysis is stopped and theelectrolyte is pressed into a 150 ml nitrogenized vessel. During thisperiod, 89 mg of Ni have dissolved anodically, corresponding to acurrent efficiency of 96% with an uptake by nickel of 2 electrons.Evaporation of the solvent under oil pump vacuum yields 5 g of a blackviscous mass. Addition of 30 ml of an ether/ethanol mixture (9/1)results in the formation of a grey-black precipitate upon vigorousshaking. The latter is allowed to set for 24 hours, whereupon the clearsupernatant is syphoned off. Washing is performed with 10 ml of pentane,and after drying under oil pump vacuum for 20 minutes, 178 mg (80% yieldbased on Ni dissolved) of a grey-black powder is obtained which isamorphous by X-ray diffraction. This powder readily dissolves in THF andtoluene, and is insoluble in diethyl ether, acetonitrile, and pentane.The colloid is very sensitive to air and moisture.

Elemental analysis: Ni: 40.05%

Transmission electron micrographs show a narrow size distribution ofcolloids which are all <10 nm in diameter and have spherical geometries.

EXAMPLE 13

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF. Since the metalcolloid is very sensitive to air and moisture, special care is to betaken that the solvents are free of water and oxygen. All operationsmust be performed under an inert gas atmosphere (argon or nitrogen).Sheets of pure cobalt (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.Under ultrasonic action, a current of 5 mA which is increased to 15 mAin the course of 20 minutes is passed between the Co electrodes. Bymeans of jacket cooling, the electrolytic cell is maintained at 16° C.In the course of the electrolysis, the electrolyte turns deep-black.After 320 C have been passed, the electrolysis is stopped and theelectrolyte is pressed into a 150 ml nitrogenized vessel. During thisperiod, 89 mg of Co have dissolved anodically, corresponding to acurrent efficiency of 96% with an uptake by cobalt of 2 electrons.Evaporation of the solvent under oil pump vacuum yields 5 g of a blackviscous mass. Addition of 30 ml of an ether/ethanol mixture (9/1)results in the formation of a grey-black precipitate upon vigorousshaking. The latter is allowed to set for 24 hours, whereupon the clearsupernatant is syphoned off. Washing is performed with 10 ml of pentane,and after drying under oil pump vacuum for 20 minutes, 178 mg (80% yieldbased on Co dissolved) of a grey-black powder is obtained which isamorphous by X-ray diffraction. This powder readily dissolves in THF,toluene, and is insoluble in diethyl ether, acetonitrile, and pentane.The colloid is very sensitive to air and moisture. Elemental analysis:Co: 39.23%

Transmission electron micrographs show a narrow size distribution ofcolloids which are all <3 nm in diameter and have spherical geometries.

EXAMPLE 14

In a multi-purpose electrolytic cell for 20-100 ml of elect-rolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF.

Since the metal colloid is very sensitive to air and moisture, specialcare is to be taken that the solvents are free of water and oxygen. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Sheets of electrolytic copper (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 5 mA which isincreased to 15 mA in the course of 20 minutes is passed between thecopper electrodes. By means of jacket cooling, the electrolytic cell ismaintained at 16° C. In the course of the electrolysis, the electrolyteturns deep-cherry to black. After 640 C have been passed, theelectrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 336 mg of Cu have dissolvedanodically, corresponding to a current efficiency of 96% with an uptakeby copper of 1 electron. Evaporation of the solvent under oil pumpvacuum yields 5.2 g of a black viscous mass. The colloid is verysensitive to air and moisture. The colloid thus obtained isredispersible in THF. When the solution is too much diluted, ananocrystalline Cu powder precipitates which is amorphous by X-raydiffraction.

Elemental analysis of the colloid: 6.4% of Cu

Elemental analysis of the powder: 98% of Cu

Transmission electron micrographs show a narrow size distribution ofcolloids which are all <10 nm in diameter and have spherical geometries.

EXAMPLE 15

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tributylhexadecylphosphonium bromide in THF. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of fine gold (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 5 mA which isincreased to 15 mA in the course of 20 minutes is passed between thegold electrodes. By means of jacket cooling, the electrolytic cell ismaintained at 16° C. In the course of the electrolysis, the electrolyteturns deep-cherry to black. After 640 C have been passed, theelectrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 1300 mg of Au have dissolvedanodically, corresponding to a current efficiency of 96% with an uptakeby gold of 1 electron. Evaporation of the solvent under oil pump vacuumleaves 6.2 g of a black viscous mass. The colloid is sensitive to airand moisture. The colloid thus obtained is redispersible in THF. Whenthe solution is too much diluted, a nanocrystalline Au powderprecipitates which is amorphous by X-ray diffraction.

Elemental analysis of the colloid: 20% of Au

Elemental analysis of the powder: 97% of Au

Transmission electron micrographs show a narrow size distribution ofcolloids which are all <12 nm in diameter and have spherical or angulargeometries.

EXAMPLE 16

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF/ACN (4/1). Sincethe metal colloid is very sensitive to air and moisture, special care isto be taken that the solvents are free of water and oxygen. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure nickel (2×2.5 cm² geometric electrodesurface area, thickness mm) at a distance of about 3 mm are used as theelectrodes. Under ultrasonic action, a current of 5 mA which isincreased to 15 mA in the course of 20 minutes is passed between thenickel electrodes. By means of jacket cooling, the electrolytic cell ismaintained at 16° C. In the course of the electrolysis, the electrolyteturns deep-black. After 320 C have been passed, the electrolysis isstopped and the electrolyte is pressed into a 150 ml nitrogenizedvessel. During this period, 89 mg of Ni have dissolved anodically,corresponding to a current efficiency of 96% with an uptake by nickel of2 electrons. Evaporation of the solvent under oil pump vacuum yields 5 gof a black viscous mass. Addition of 30 ml of an ether/ethanol mixture(9/1) results in the formation of a grey-black precipitate upon vigorousshaking. The latter is allowed to set for 24 hours, whereupon the clearsupernatant is syphoned off. Washing is performed with 10 ml of pentane,and after drying under oil pump vacuum for 20 minutes, 178 mg (80% yieldbased on Ni dissolved) of a grey-black powder is obtained. This powderreadily dissolves in THF and toluene, and is insoluble in diethyl ether,acetonitrile, and pentane. The colloid is very sensitive to air andmoisture.

Elemental analysis: Ni: 36.46%; C: 28.29%; H: 4.01%; N: 13.22%; Br:2.72%.

Transmission electron micrographs show a narrow size distribution ofcolloids which are all ≦6 nm in diameter and have spherical geometries.

EXAMPLE 17

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 60 ml of 0.2M tetrabutylammonium bromide in ACN. All operationsmust be performed under an inert gas atmosphere (argon or nitrogen). Twosheets of pure platinum (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.Under ultrasonic action, a current of 30 mA which is increased to 100 mAin the course of 20 minutes is passed between the platinum electrodes.By means of jacket cooling, the electrolytic cell is maintained at 30°C. In the course of the electrolysis, the electrolyte turns deep-black.After 3200 C have been passed, the electrolysis is stopped and theelectrolyte is pressed into a 150 ml nitrogenized vessel. During thisperiod, 330 mg of Pt have dissolved anodically, corresponding to acurrent efficiency of 10% with an uptake by platinum of 2 electrons.Addition of 30 ml of oxygen-free water results in the formation of agrey-black precipitate upon Vigorous shaking. The latter is allowed toset for 24 hours, whereupon the clear supernatant is syphoned off.Drying under oil pump vacuum yields 410 mg of a grey-black powder whichis amorphous by X-ray diffraction. It very readily dissolves in ACN andDMF, and is insoluble in THF, diethyl ether, pentane, water, andtoluene. Elemental analysis: 80% of Pt

Transmission electron micrographs show a narrow size distribution of Ptcolloids in a size range of ≦2 nm.

EXAMPLE 18

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 60 ml of 0.2M tetrabutylammonium chloride in ACN. All operationsmust be performed under an inert gas atmosphere (argon or nitrogen). Twosheets of pure rhodium (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a disingenuously about 3 mm are used as theelectrodes. Under ultrasonic action, a current of 20 mA which isincreased to 75 mA in the course of 20 minutes is passed between therhodium electrodes. By means of jacket cooling, the electrolytic cell ismaintained at 30° C. In the course of the electrolysis, the electrolyteturns deep-black. After 800 C have been passed, the electrolysis isstopped and the electrolyte is pressed into a 150 ml nitrogenizedvessel. During this period, 207 mg of Rh have dissolved anodically,corresponding to a current efficiency of 25% with an uptake by rhodiumof 1 electron. Addition of 30 ml of oxygen-free water results in theformation of a grey-black precipitate upon vigorous shaking. The latteris allowed to set for 24 hours, whereupon the clear supernatant issyphoned off. Drying under oil pump vacuum yields 2900 mg of agrey-black powder which is amorphous by X-ray diffraction. It veryreadily dissolves in ACN and DMF, and is insoluble in THF, diethylether, pentane, water, and toluene.

Elemental analysis: 70% of Rh

Transmission electron micrographs show a narrow size distribution of Rhcolloids in a size range of ≦2 nm.

EXAMPLE 19

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 60 ml of 0.2M tetrabutylammonium hexafluorophosphate in DME. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure rhodium (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 30 mA which isincreased to 100 mA in the course of 20 minutes is passed between therhodium electrodes. By means of jacket cooling, the electrolytic cell ismaintained at 30° C. In the course of the electrolysis, the electrolyteturns deep-black. After 800 C have been passed, the electrolysis isstopped and the electrolyte is pressed into a 150 ml nitrogenizedvessel. During this period, 207 mg of Rh have dissolved anodically,corresponding to a current efficiency of 25% with an uptake by rhodiumof 1 electron. Addition of 30 ml of oxygen-free water results in theformation of a grey-black precipitate upon vigorous shaking. The latteris allowed to set for 24 hours, whereupon the clear supernatant issyphoned off. Drying under oil pump vacuum yields 258 mg of a grey-blackpowder which is amorphous by X-ray diffraction. It very readilydissolves in ACN and DMF, and is insoluble in THF, diethyl ether,pentane, water, and toluene.

Elemental analysis: 80% of Rh

Transmission electron micrographs show a narrow size distribution of Rhcolloids in a size range of ≦2 nm.

EXAMPLE 20

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 60 ml of 0.2M tetrabutylammonium hexafluorophosphate in DME. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure platinum (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 30 mA which isincreased to 100 mA in the course of 20 minutes is passed between theplatinum electrodes. By means of jacket cooling, the electrolytic cellis maintained at 30° C. In the course of the electrolysis, theelectrolyte turns deep-black. After 100 C have been passed, theelectrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 330 mg of Pt have dissolvedanodically, corresponding to a current efficiency of 30% with an uptakeby platinum of 2 electrons. Addition of 30 ml of oxygen-free waterresults in the formation of a grey-black precipitate upon vigorousshaking. The latter is allowed to set for 24 hours, whereupon the clearsupernatant is syphoned off. Drying under oil pump vacuum yields 410 mgof a grey-black powder which is amorphous by X-ray diffraction. It veryreadily dissolves in ACN and DMF, and is insoluble in THF, diethylether, pentane, water, and toluene.

Elemental analysis: 80% of Pt

Transmission electron micrographs show a narrow size distribution of Ptcolloids in a size range of ≦2 nm.

EXAMPLE 21

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF/ACN (4/1). Sincethe metal colloid is very sensitive to air and moisture, special care isto be taken that the solvents are free of water and oxygen. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure nickel (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. Under ultrasonic action, a current of 6 mA is passedbetween the nickel electrodes. By means of jacket cooling, theelectrolytic cell is maintained at 16° C. In the course of theelectrolysis, the electrolyte turns deep-black. After 320 C have beenpassed, the electrolysis is stopped and the electrolyte is pressed intoa 150 ml nitrogenized vessel. During this period, 89 mg of Ni havedissolved anodically, corresponding to a current efficiency of 96% withan uptake by nickel of 2 electrons. Evaporation of the solvent under oilpump vacuum yields 5 g of a black viscous mass. Addition of 30 ml of anether/ethanol mixture (9/1) results in the formation of a grey-blackprecipitate upon vigorous shaking. The latter is allowed to set for 24hours, whereupon the clear supernatant is syphoned off. Washing isperformed with 10 ml of pentane, and after drying under oil pump vacuumfor 20 minutes, 178 mg (80% yield based on Ni dissolved) of a grey-blackpowder is obtained. This powder readily dissolves in THF and toluene,and is insoluble in diethyl ether, acetonitrile, and pentane. Thecolloid is very sensitive to air and moisture.

Elemental analysis: 60% of Ni

Transmission electron micrographs show a broader size distribution ofcolloids which are all <30 nm in diameter and have spherical orpolyhedral geometries. The colloid particles are significantly largerthan those in example 16 where a lower current density has been employed(cf.examples 2 through 4: Pd).

EXAMPLE 22

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in THF. All operationsmust be performed under an inert gas atmosphere (argon or nitrogen). Twosheets of fine silver (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.Under ultrasonic action, a current of 5 mA which is increased to 15 mAin the course of 20 minutes is passed between the silver electrodes. Bymeans of jacket cooling, the electrolytic cell is maintained at 16° C.In the course of the electrolysis, the electrolyte turns deep-cherry toblack. After 640 C have been passed, the electrolysis is stopped and theelectrolyte is pressed into a 150 ml nitrogenized vessel. During thisperiod, 712 mg of Ag have dissolved anodically, corresponding to acurrent efficiency of 96% with an uptake by silver of 1 electron.Evaporation of the solvent under oil pump vacuum leaves 700 mg of ablack viscous mass. The colloid is sensitive to air and moisture. Thenanocrystalline powder thus obtained is not redispersible in THF.

Elemental analysis of the powder: 93% of Ag

Transmission electron micrographs show a narrow size distribution ofagglomerated particles which are all ≦12 nm in diameter and havespherical or hexagonal geometries.

EXAMPLE 23

Experimental protocol for the preparation of a Pd/Ni bimetallic colloid

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 80 ml of 0.1M tetraoctylammonium bromide in THF. A sheet of pureplatinum (5×5 cm² geometric electrode surface area) is used as thecathode. An electrode of pure nickel and an electrode of pure palladium(2.5×5 cm² geometric electrode surface area) which are placed side byside at a distance of 4 mm to the cathode are both used as anodes. Alloperations must be performed under an inert gas atmosphere (argon); allsolvents must be thoroughly dried and freshly destilled. At atemperature of 30° C. and under ultrasonic action, a current of 30 mA ispassed between nickel and platinum as well as between palladium andplatinum by means of a double power supply unit, so both currents can becontrolled independently. In the course of the electrolysis, thesolution turns deep-brown to black. After a total of 1 Ah has beenpassed, the electrolysis is stopped. During this period, 350 mg ofnickel (=65% current efficiency) and 600 mg of palladium (=61% currentefficiency) have dissolved. The solvent is evaporated and the tackyresidue is dried under a good oil pump vacuum. The black residue thusobtained is washed first with 50 ml of pentane and thereafter 5 timeswith 40 ml of an ethanol/pentane mixture (1.5/10). After drying underoil pump vacuum, 1.1 g of a grey-black powder is obtained. This powdervery readily dissolves in THF and acetone, is less soluble in tolueneand ethanol, and insoluble in ether, pentane, acetonitrile, and water.

The THF colloid solutions thus obtained are stable for months.

Transmission electron micrographs show well-separated, sphericallyshaped colloids in a size range of from 0.5 to 4 nm. EnergydispersiveX-ray spot analyses (EDX) reveal that almost all of the colloidparticles contain both metals. Investigations by elemental analysisindicate a Pd/Ni ratio of 42/18.

EXAMPLE 24

Experimental protocol for the preparation of a Pd/Ni bimetallic colloid

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 80 ml of 0.1M tetraoctylammonium bromide in THF. A sheet of pureplatinum (5×5 cm² geometric electrode surface area) is used as thecathode. An electrode of pure nickel and an electrode of pure palladium(2.5×5 cm² geometric electrode surface area) which are placed side byside at a distance of 4 mm to the cathode are both used as anodes. Alloperations must be performed under an inert gas atmosphere (argon); allsolvents must be thoroughly dried and freshly destilled. At atemperature of 30° C. and under ultrasonic action, a current of 30 mA ispassed between nickel and platinum and a current of 5 mA is passedbetween palladium and platinum by means of a double power supply unit,so both currents can be controlled independently. In the course of theelectrolysis, the solution turns deep-brown to black. After a total of 1Ah has been passed, the electrolysis is stopped. During this period, 670mg of nickel (=80% current efficiency) and 290 mg of palladium (=90%current efficiency) have dissolved. The same product is observed if ananode made of an alloy with a Pd/Ni ratio of 5/25 is employed. Thesolvent is evaporated and the tacky residue is dried under a good oilpump vacuum. The black residue thus obtained is washed first with 50 mlof pentane and thereafter 5 times with 40 ml of an ethanol/pentanemixture (1.5/10). After drying under oil pump vacuum, 1.1 g of agrey-black powder is obtained. This powder very readily dissolves in THFand acetone, is less soluble in toluene and ethanol, and insoluble inether, pentane, acetonitrile, and water. The THF colloid solutions thusobtained are stable for months. Transmission electron micrographs showwell-separated, spherically shaped colloids in a size range of from 0.5to 4 nm. EDX spot analyses reveal that almost all of the colloidparticles contain both metals. Investigations by elemental analysisindicate a Pd/Ni ratio of 5/25. When this is compared to the results ofexample 23, it can be seen that the colloid composition can becontrolled through the relative currents passing through the two metalanodes.

EXAMPLE 25

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in toluene. Two sheetsof pure palladium (2×2.5 cm² geometric electrode surface area, thickness1 mm) at a distance of about 3 mm are used as the electrodes. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). With vigorous stirring by means of a magnetic stirrer or withthe use of ultrasonic waves, a current of 5 mA which is increased to 17mA in the course of 10 min is passed between the palladium electrodes.By means of a jacket heating, the electrolytic cell is maintained at60°-130° C. In the course of the electrolysis, the electrolyte turnsdeep-black. After a charge of 640 C has been passed, the electrolysis isstopped and the electrolyte is pressed into a 150 ml nitrogenizedvessel. During this period, 300 mg of palladium have dissolvedanodically, corresponding to an anodic efficiency of 90%. Evaporation ofthe solvent under oil pump vacuum leaves 4.4 g of a black solid. This iswashed 3 times with 40-50 ml of an ethanol/pentane mixture (3/7) toyield 360 mg of a grey-black powder which is amorphous by X-raydiffraction. This powder readily dissolves in THF, acetone and toluene,and is insoluble in water, diethyl ether, and pentane.

Elemental analysis: Pd 72.5%; the residual 27.5% consists oftetraoctylammonium bromide protecting the particles as a colloidstabilizer.

Transmission electron micrographs show a narrow size distribution ofcolloids which are all ≦5 nm in diameter and have spherical geometries.

EXAMPLE 26

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctadecylammoniumbromide in THF. The saltwill dissolve completely if the electrolytic vessel is maintained at atemperature of 60° C. Two sheets of pure palladium (2×2.5 cm² geometricelectrode surface area, thickness 1 mm) at a distance of about 3 mm areused as the electrodes. All operations must be performed under an inertgas atmosphere (argon or nitrogen). With vigorous stirring by means of amagnetic stirrer or with the use of ultrasonic waves, a current of 5 mAwhich is increased to 17 mA in the course of 10 min is passed betweenthe palladium electrodes. By means of a jacket heating, the electrolyticcell is maintained at 60° C. In the course of the electrolysis, theelectrolyte turns deep-black. After a charge of 640 C has been passed,the electrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 300 mg of palladium havedissolved anodically, corresponding to an anodic efficiency of 90% withan uptake by palladium of 2 electrons. Evaporation of the solvent underoil pump vacuum leaves 9.5 g of a black solid. This is dissolved in 60ml of toluene to which 30 ml of an ethanol/water mixture (6/1) is added.After vigorous shaking, a brown-grey precipitate forms. This is allowedto set for 24 hours, whereupon the clear supernatant is syphoned off.Drying under oil pump vacuum for 20 minutes yields 500 mg (95% yieldbased on palladium dissolved) of a grey-black powder which is amorphousby X-ray diffraction. This powder readily dissolves in pentane andtoluene, is poorly soluble in THF and insoluble in water and acetone.

Elemental analysis: 58.8% of Pd; the residual 41.2% consists oftetraoctadecylammonium bromide protecting the particles as a colloidstabilizer.

Transmission electron micrographs show a narrow size distribution ofcolloids which are all ≦6 nm in diameter and have spherical geometries.The solubilities of the colloid powders depend on the protective colloidemployed and can be adjusted within a selected range from water solubleto pentane soluble:

    ______________________________________                                                          solubility of colloid                                                                       Example                                       protective colloid employed                                                                     powder        No.                                           ______________________________________                                        (dimethyldodecylammonio)-                                                                       water > ethanol                                                                             8                                             propanesulfonate                                                              tetrabutylammonium bromide                                                                      DMF > THF     10                                            tetrabutylammonium bromide                                                                      THF > toluene 1                                             tetradodecylammonium bromide                                                                    toluene > THF 9                                             tetraoctadecylammonium                                                                          pentane >     26                                            bromide           toluene > THF                                               ______________________________________                                    

EXAMPLE 27

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium perchlorate in THF. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Two sheets of pure palladium (2×2.5 cm² geometric electrodesurface area, thickness 1 mm) at a distance of about 3 mm are used asthe electrodes. With vigorous stirring or with the use of ultrasonicwaves, a current of 5 mA which is increased to 17 mA in the course of 20min is passed between the palladium electrodes. By means of jacketcooling, the electrolytic cell is maintained at 16° C. In the course ofthe electrolysis, the electrolyte turns deep-black and a grey-brownpowder precipitates. After a charge of 640 C has been passed, theelectrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 300 mg of palladium havedissolved anodically, corresponding to an anodic efficiency of 90%. Theprecipitate is allowed to set for 24 hours, whereupon the brownsupernatant is syphoned off. After drying under oil pump vacuum for 20minutes, 320 mg of a grey-black solid is obtained which consists ofagglomerated Pd particles having sizes of ≦8 nm according totransmission electron micrographs. Elemental analysis indicates a Pdcontent of 92% (the remainder is tetraoctylammonium perchlorate). Thepowder thus obtained is not completely soluble in THF or other solvents,however, which indicates poor wetting of the colloid particles by thestabilizer. The same results have been obtained with other large,non-coordinating anions, such as BF₄ ⁻. Coordinating anions, such ase.g. halogenide, are crucial to the stabilization of the colloids andhence redispersibility.

EXAMPLE 28

Preparation of a colloid with chiral protective shell--chirality at thequaternary N atom

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M butylbenzyloctyldodecylammoniumbromide in THF. Twosheets of pure palladium (2×2.5 cm² geometric electrode surface area,thickness 1 mm) at a distance of about 3 mm are used as the electrodes.All operations must be performed under an inert gas atmosphere (argon ornitrogen). With vigorous stirring by means of a magnetic stirrer or withthe use of ultrasonic waves, a current of 5 mA which is increased to 17mA in the course of 10 min is passed between the palladium electrodes.By means of a jacket heating, the electrolytic cell is maintained at 30°C. In the course of the electrolysis, the electrolyte turns deep-black.After a charge of 640 C has been passed, the electrolysis is stopped andthe electrolyte is pressed into a 150 ml nitrogenized vessel. Duringthis period, 300 mg of palladium have dissolved anodically,corresponding to an anodic efficiency of 90%. Addition of 25 ml ofoxygen-free water results in the formation of a brown-grey precipitate.This is allowed to set for 24 hours, whereupon the clear supernatant issyphoned off. After drying under oil pump vacuum, 350 mg of a grey-blacksolid is obtained. This solid readily dissolves in THF and toluene, andis insoluble in water and pentane.

Elemental analysis: 72% of Pd; the residual 28% consists ofbutylbenzyloctyldodecylammoniumbromide protecting the particles as acolloid stabilizer.

Transmission electron micrographs show a narrow size distribution of Pdcolloids which are all <4 nm in diameter.

EXAMPLE 29

Preparation of a colloid with chiral protective shell--chirality in theside chain

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tributyl(1-methylbenzyl)ammonium bromide in THF.Two sheets of pure palladium (2×2.5 cm² geometric electrode surfacearea, thickness 1 mm) at a distance of about 3 mm are used as theelectrodes. All operations must be performed under an inert gasatmosphere (argon or nitrogen). With vigorous stirring by means of amagnetic stirrer or with the use of ultrasonic waves, a current of 5 mAwhich is increased to 17 mA in the course of 10 min is passed betweenthe palladium electrodes. By means of a jacket heating, the electrolyticcell is maintained at 35° C. In the course of the electrolysis, theelectrolyte turns deep-black and a brown-grey precipitate forms. After acharge of 640 C has been passed, the electrolysis is stopped and theelectrolyte is pressed into a 150 ml nitrogenized vessel. During thisperiod, 300 mg of palladium have dissolved anodically, corresponding toan anodic efficiency of 90%. The precipitate is allowed to set for 24hours, whereupon the clear supernatant is syphoned off. After dryingunder oil pump vacuum, 310 mg of a grey-black solid is obtained. Thissolid dissolves readily in DMF and poorly in THF, but is insoluble inwater and pentane.

Elemental analysis: 74% of Pd; the residual 26% consists oftributyl(1-methylbenzyl)ammonium bromide protecting the particles as acolloid stabilizer. Transmission electron micrographs show a narrow sizedistribution of Pd colloids which are all ≦6 nm in diameter.

EXAMPLE 30

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetraoctylammonium bromide in2,5-dimethyltetrahydrofuran. Two sheets of pure palladium (2×2.5 cm²geometric electrode surface area, thickness 1 mm) at a distance of about3 mm are used as the electrodes. All operations must be performed underan inert gas atmosphere (argon or nitrogen). With vigorous stirring bymeans of a magnetic stirrer, a current of 5 mA which is increased to 17mA in the course of 10 min is passed between the palladium electrodes.By means of a jacket heating, the electrolytic cell is maintained at 39°C. In the course of the electrolysis, the electrolyte turns brown and abrown-grey precipitate forms. After a charge of 640 C has been passed,the electrolysis is stopped and the electrolyte is pressed into a 150 mlnitrogenized vessel. During this period, 300 mg of palladium havedissolved anodically, corresponding to an anodic efficiency of 90%. Theprecipitate is allowed to set for 3 hours at 39° C., whereupon theslightly brown supernatant is syphoned off. After drying under oil pumpvacuum, 350 mg of a grey-black solid is obtained. This solid readilydissolves in THF and toluene, and is insoluble in water and pentane. Thecourse of the experiment is analogous with Ni, Co, and Fe.

Elemental analysis: 72% of Pd; the residual 28% consists oftetraoctylammonium bromide protecting the particles as a colloidstabilizer.

Transmission electron micrographs show a narrow size distribution of Pdcolloids which are all <2 nm in diameter.

EXAMPLE 31

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetrabutylammonium acetate in THF. Two sheets ofpure platinum (1.5×2 cm² geometric electrode surface area, thickness 0.5mm) at a distance of about 3 mm are used as the electrodes. Alloperations must be performed under an inert gas atmosphere (argon ornitrogen). Under ultrasonic action, 0.5 g of PtCl₂ is dissolved in theelectrolyte and a current of 5 mA which is increased to 30 mA in thecourse of 10 min is passed between the platinum electrodes. By means ofjacket cooling, the electrolytic cell is maintained at 20° C. In thecourse of the electrolysis, the electrolyte turns deep-black. After acharge of 365 C has been passed, the electrolysis is stopped and theelectrolyte is pressed into a 200 ml nitrogenized vessel. Within 2-5hours, a grey-black precipitate forms. The slightly brown clearsupernatant is pressed off under inert gas and the precipitate is washedtwice with 10 ml of diethyl ether. Drying under oil pump vacuum for onehour yields 645 mg of a grey-black powder. This powder readily dissolvesin DMF, and is insoluble in water, diethyl ether, THF, acetonitrile,toluene, and pentane.

Elemental analysis: 51% of platinum. The remainder consists of theammonium salt. This corresponds to-an efficiency of 90% with an uptakeof 2 electrons per platinum ion. Transmission electron micrographs showa narrow size distribution of colloids which are all 3-5 nm in diameterand have spherical geometries. Comparative TEM/STM investigations ofthese colloids (adsorbed from a DMF solution, substrate 200 nm gold onTempax quartz carrier) clearly show coating of the metal cores with amonomolecular layer of stabilizer. Electrolyses with PtBr₂, PtI₂, andplatinum(II) acetylacetonate proceed in much the same way.

EXAMPLE 32

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.1M tetrabutylammonium acetate in THF/ACN (4/1).Metal salt: 0.5 g of PdCl₂. Current: 5 mA, increased to 20 mA in thecourse of 10 minutes. Charge passed: 500 C. Product: 440 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 62% of palladium. Yield 93%. Size: <5 nm.Electrolyses with PdBr₂, PdI₂, and palladium(II) acetylacetonate proceedin much the same way.

EXAMPLE 33

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.1M tetrabutylammonium trifluoroacetate in THF.Metal salt: 0.5 g of PdCl₂. Charge passed: 500 C. Product: 458 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 54% of palladium. Yield 84%. Diameter <5 nm.Electrolyses with PdBr₂, PdI₂, and palladium(II) acetylacetonate proceedin much the same way.

EXAMPLE 34

The procedure and processing are analogous to that of Example 31.Electrolyte: 50 ml of 0.1M tetraoctylammonium bromide in THF. Metalsalt: 50 ml of 0.05M Mo₂ (OAc)₄ in THF. Charge passed: 480 C. Theelectrolyte is pressed into a 200 ml nitrogenized vessel and addition of20 ml of diethyl ether results in the formation of a grey-blackprecipitate upon vigorous shaking. Product: 265 mg of a black powder.This powder readily dissolves in THF and toluene, and is insoluble inwater, diethyl ether, DMF, acetonitrile, and pentane.

Elemental analysis: 37% of molybdenum. Yield 72%. Diameter: 1-5 nm.Electrolyses with Noct₄ Cl, Noct₄ ClO₄, Noct₄ PF₆, Noct₄ BF₄, Noct₄ OTf,Noct₄ OTs, Poct₄ Cl, or Poct₄ Br as the stabilizer proceed in much thesame way.

EXAMPLE 35

The procedure and processing are analogous to that of Example 31.Electrolyte: 50 ml of 0.1M tetrabutylammonium acetate in THF, and 50 mlof 0.1M tetrabutylammonium chloride in THF. Metal salt: 0.5 g of RhCl₃•xH₂ O. Charge passed: 700 C. Product: 440 mg of a grey-black powder.This powder readily dissolves in DMF, and is insoluble in water, diethylether, THF, acetonitrile, toluene, and pentane.

Elemental analysis: 46% of rhodium. Yield: 92%. Diameter: 2-3 nm.Electrolyses with RhBr₃ •xH₂ O and RhCl₃ proceed in much the same way.

EXAMPLE 36

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of RuCl₃ •H₂ O. By means of jacketcooling, the electrolytic cell is maintained at 18° C. Charge passed:650 C. Within 24 hours, a grey-black precipitate forms. Product: 290 mgof a grey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 55% of ruthenium. Yield: 73%. Diameter: <5 nm.Electrolyses with RuCl₃ proceed in much the same way.

EXAMPLE 37

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of CoBr₂. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 400 C. Theslightly brown clear supernatant is pressed off under inert gas and theprecipitate is washed twice with 10 ml of absolute pentane. Product: 250mg of a grey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 44% of cobalt. Yield: 88%. Diameter: <5 nm.Electrolyses with CoI₂ proceed in much the same way.

EXAMPLE 38

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of NiBr₂. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 500 C. Theslightly brown clear supernatant is pressed off under inert gas and theprecipitate is washed twice with 10 ml of absolute pentane. Product: 250mg of a grey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 38% of nickel. Yield: 86%. Diameter: <5 nm.Electrolyses with NiI₂ proceed in much the same way.

EXAMPLE 39

The procedure and processing are analogous to that of Example 31. Metalsalt: 0.5 g of OsCl₃. By means of jacket cooling, the electrolytic cellis maintained at 18° C. Current: 5 mA, increased to 5 mA in the courseof 5 minutes. Charge passed: 500 C. Within 24 hours, a grey-blackprecipitate forms. Product: 360 mg of a grey-black powder. This powderreadily dissolves in DMF, and is insoluble in water, diethyl ether, THF,acetonitrile, toluene, and pentane.

Elemental analysis: 62% of osmium. Yield: 69%. Diameter: <3 nm.

EXAMPLE 40

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.05M tetrabutylammoniumacetate in THF. Metalsalt: 0.5 g of Pd(OAc)₂. Current: 2 mA, increased to 30 mA in the courseof 10 minutes. Charge passed: 430 C. Product: 318 mg of a black powder.This powder readily dissolves in DMF, and is insoluble in water, diethylether, THF, acetonitrile, toluene, and pentane.

Elemental analysis: 70% of palladium. Yield: 95%. Diameter: 1-5 nm.Electrolyses with Pd(II) trifluoroacetate and Pd(II)trifluoromethanesulfonate proceed in much the same way.

EXAMPLE 41

The procedure and processing are analogous to that of Example 31. Metalsalt: 0.6 g of GaBr₃. Current: 2 mA, increased to 20 mA in the course of10 minutes. Charge passed: 550 C. Product: 195 mg of a black powder.This powder readily dissolves in DMF, and is insoluble in water, THF,diethyl ether, toluene, acetonitrile, and pentane.

Elemental analysis: 61% of gallium. Yield: 89%. Diameter: <10 nm.Electrolyses with GaCl₃ proceed in much the same way.

EXAMPLE 42

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 100 ml of 0.1M tetraoctylammonium bromide in THF.

Two sheets of pure platinum (1.5×2 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. All operations must be performed under an inert gasatmosphere (argon or nitrogen). Under ultrasonic action, 0.6 g ofIn(OAc)₃ is dissolved in the electrolyte and a current of 2 mA which isincreased to 20 mA in the course of 10 min is passed between theplatinum electrodes. By means of jacket cooling, the electrolytic cellis maintained at 20° C. In the course of the electrolysis, theelectrolyte turns deep-black. After a charge of 600 C has been passed,the electrolysis is stopped and the electrolyte is pressed into a 200 mlnitrogenized vessel. Addition of 15 ml of oxygen-free water to theelectrolyte results in the formation of a grey-black precipitate uponvigorous shaking. After 24 hours, the slightly brown clear supernatantis pressed off under inert gas and the precipitate is washed twice with10 ml of diethyl ether. Drying under oil pump vacuum for 24 hours yields380 mg of a black powder. This powder readily dissolves in THF andtoluene, and is insoluble in water, diethyl ether, DMF, acetonitrile,and pentane.

Elemental analysis: 55% of indium. This corresponds to an efficiency of89% with an uptake of 3 electrons per indium ion. Transmission electronmicrographs show a size distribution of colloids which are all <10 nm indiameter and have spherical geometries. Electrolyses with Noct₄ Cl,Noct₄ ClO₄, Noct₄ PF₆, Noct₄ BF₄, Noct₄ OTf, Noct₄ OTs, Poct₄ Cl, orPoct₄ Br as the stabilizer proceed in much the same way.

EXAMPLE 43

The procedure and processing are analogous to that of Example 31. Metalsalt: 0.5 g of Tl(OAc)₃. Charge passed: 370 C. Product: 530 mg of ablack powder. This powder readily dissolves in DMF, and is insoluble inwater, THF, diethyl ether, toluene, acetonitrile, and pentane.

Elemental analysis: 36% of thallium. Yield: 72%. Diameter: 1-5 nm.

EXAMPLE 44

The procedure and processing are analogous to that of Example 42. Metalsalt: 0.5 g of Pd(OAc)₂. Charge passed: 430 C. Product: 288 mg of ablack powder. This powder readily dissolves in THF and toluene, and isinsoluble in water, diethyl ether, DMF, acetonitrile, and pentane.

Elemental analysis: 72% of palladium. Yield: 88%. Diameter: 3-4 nm.Comparative TEM/STM investigations of these colloids (adsorbed from aTHF solution, substrate: 200 nm gold on Tempax quartz carrier) clearlyshow coating of the metal cores with a monomolecular layer ofstabilizer. Electrolyses with Noct₄ Cl, Noct₄ ClO₄, Noct₄ PF₆, Noct₄BF₄, Noct₄ OTf, Noct₄ OTs, Poct₄ Cl or Poct₄ Br as the stabilizerproceed in much the same way.

EXAMPLE 45

The procedure and processing are analogous to that of Example 42.Electrolyte: 100 ml of 0.1M tetraoctylammonium bromide in THF/water(10/1). Metal salt: 0.5 g of PtBr₂. Charge passed: 270 C. Product: 420mg of a black powder. This powder readily dissolves in THF and toluene,and is insoluble in water, diethyl ether, DMF, acetonitrile, andpentane.

Elemental analysis: 41% of platinum. Yield: 63%. Diameter: 1-10 nm.Electrolyses with Noct₄ Cl, Noct₄ ClO₄, Noct₄ PF₆, Noct₄ BF₄, Noct₄ OTf,Noct₄ OTs, Poct₄ Cl, or Poct₄ Br as the stabilizer proceed in much thesame way.

EXAMPLE 46

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.1M tetrabutylammonium bromide in THF. Metalsalt: 0.5 g of Pd(OAc)₂. Charge passed: 430 C. Product: 294 mg of ablack powder. This powder very readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 71% of palladium. Yield: 89%. Diameter: 3-4 nm.Comparative TEM/STM investigations of these colloids (adsorbed from aDMF solution, substrate: 200 nm gold on Tempax quartz carrier) clearlyshow coating of the metal cores with a monomolecular layer ofstabilizer. Electrolyses with NBu₄ Cl, NBu₃ I, NBu₄ ClO₄, NBu₄ PF₆, NBu₄BF₄, NBu₄ OTf, NBu₄ OTs, PBu₄ Cl, or PBu₄ Br as the stabilizer proceedin much the same way.

EXAMPLE 47

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 100 ml of 0.1M tetraoctadecylammonium bromide in THF,thermostated at 60° C. Two sheets of pure platinum (1.5×2 cm² geometricelectrode surface area, thickness 0.5 mm) at a distance of about 3 mmare used as the electrodes. All operations must be performed under aninert gas atmosphere (argon or nitrogen). Under ultrasonic action orwith vigorous stirring by means of a magnetic stirrer, 0.5 g of Pd(OAc)₂is dissolved in the electrolyte and a current of 2 mA which is increasedto 10 mA in the course of 10 min is passed between the platinumelectrodes. By means of a jacket heating, the electrolytic cell ismaintained at 60° C. in order to keep the stabilizer in solution. In thecourse of the electrolysis, the electrolyte turns deep-black. After acharge of 430 C has been passed, the electrolysis is stopped and theelectrolyte is pressed into a 200 ml nitrogenized vessel. Evaporation ofthe solvent under oil pump vacuum leaves a black solid. This isdissolved in 100 ml of toluene and 20 ml of an ethanol/water mixture(10/1) is slowly added. Upon vigorous shaking, a grey-black precipitateforms. After 24 hours, the slightly brown clear supernatant is pressedoff under inert gas and the precipitate is washed twice with 10 ml ofdiethyl ether. Drying under oil pump vacuum for 24 hours yields 457 mgof a grey powder. This powder readily dissolves in toluene and pentane,and is insoluble in water, diethyl ether, DMF, THF, and acetonitrile.

Elemental analysis: 34% of palladium. This corresponds to an efficiencyof 66% with an uptake of 2 electrons per palladium ion. Transmissionelectron micrographs show a size distribution of colloids which are all1-5 nm in diameter and have spherical geometries. Comparative TEM/STMinvestigations of these colloids (adsorbed from a pentane solution,substrate: 200 nm gold on Tempax quartz carrier) clearly show coating ofthe metal cores with a monomolecular layer of stabilizer.

EXAMPLE 48

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.1M tetrabutylammonium butanoate in THF. Metalsalt: 0.5 g of PtBr₂. Charge passed: 270 C. Product: 316 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 79% of platinum. Yield: 91%. Diameter: 1-10 nm.Electrolyses with PtCl₂, PtI₂, and platinum(II) acetylacetonate proceedin much the same way.

EXAMPLE 49

The procedure and processing are analogous to that of Example 42.Electrolyte: 100 ml of 0.1M tetraoctylammonium propanoate in THF. Metalsalt: 0.5 g of PtCl₂. Charge passed: 370 C. Product: 508 mg of agrey-black powder. This powder readily dissolves in THF and toluene, andis insoluble in water, diethyl ether, DMF, acetonitrile, and pentane.

Elemental analysis: 71% of platinum. Yield: 98%. Diameter: 1-10 nm.Electrolyses with PtBr₂, PtI₂, and platinum(II) acetylacetonate proceedin much the same way.

EXAMPLE 50

The procedure and processing are analogous to that of Example 42.Electrolyte: 100 ml of 0.1M (-)-N-dodecyl-N-methylephedrinium bromide inTHF. Metal salt: 0.5 g of Pd(OAc)₂. Charge passed: 430 C. Product: 325mg of a grey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 65% of palladium. Yield: 90%. Diameter: 1-5 nm. NMRspectroscopic studies clearly show the signals of the stabilizer.

EXAMPLE 51

The procedure and processing are analogous to that of Example 42.Electrolyte: 100 ml of 0.1M benzylbutyldodecyloctylammonium bromide inTHF. Metal salt: 0.5 g of Pd(OAc)₂. Charge passed: 430 C. Product: 274mg of a grey-black powder. This powder readily dissolves in THF andtoluene, and is insoluble in water, diethyl ether, DMF, acetonitrile,and pentane.

Elemental analysis: 78% of palladium. Yield: 91%. Diameter: 1-5 nm. NMRspectroscopic studies clearly show the signals of the stabilizer.Electrolyses with tributyl(1-methylbenzyl)ammonium bromide as thestabilizer proceed in much the same way.

EXAMPLE 52

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.1M3-(dimethyldodecylammonio)propanesulfonate•LiCl in THF. Metal salt: 0.5g of Pd(OAc)₂. Current: 2 mA, increased to 15 mA in the course of 10minutes. By means of jacket cooling, the electrolytic cell is maintainedat 40° C. Charge passed: 430 C. Product: 402 mg of a grey-black powder.This powder readily dissolves in water, methanol and ethanol, and isinsoluble in THF, toluene, diethyl ether, DMF, acetonitrile, andpentane.

Elemental analysis: 52% of palladium. Yield: 89%. Diameter: 1-10 nm.Electrolyses with 3-(N,N-dimethylstearylammonio)propanesulfonate as thestabilizer proceed in much the same way. Comparative TEM/STMinvestigations of these colloids (adsorbed from an aqueous solution,substrate: 200 nm gold on Tempax quartz carrier) clearly show coating ofthe metal cores with a monomolecular layer of stabilizer. Survey of thesolubilities of differently stabilized colloids:

    ______________________________________                                        Example                                                                              stabilizer        colloid is soluble in                                ______________________________________                                        52     (dimethyldodecylammonio)-                                                                       water > ethanol                                             propanesulfonate                                                       31     tetrabutylammonium . . .                                                                        DMF > THF                                            34     tetraoctylammonium . . .                                                                        THF > toluene                                        47     tetraoctadecylammonium . . .                                                                    pentane > toluene >                                                           THF                                                  ______________________________________                                    

EXAMPLE 53

The procedure and processing are analogous to that of Example 52.Electrolyte: 100 ml of 0.1M3-(dimethyldodecylammonio)propanesulfonate•LiOAc in THF. Metal salt: 0.5g of RuCl₃ •H₂ O. Charge passed: 650 C. Product: 270 mg of a blackpowder. This powder very readily dissolves in water, and is insoluble inDMF, diethyl ether, THF, acetonitrile, toluene, and pentane.

Elemental analysis: 58% of ruthenium. Yield: 75%. Diameter: 1-2 nm.Comparative TEM/STM investigations of these colloids (adsorbed from anaqueous solution, substrate: 200 nm gold on Tempax quartz carrier)clearly show coating of the metal cores with a monomolecular layer ofstabilizer.

EXAMPLE 54

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.05M tetrabutylammonium bromide in propylenecarbonate. Metal salt: 0.5 g of Pd(OAc)₂. Charge passed: 430 C. Product:550 mg of a black powder. This powder very readily dissolves in DMF, andis insoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 41% of palladium. Yield: 96%. Diameter: 1-5 nm.Electrolyses with NBu₄ Cl, NBu₄ I, NBu₄ ClO₄, NBu₄ PF₆, NBu₄ BF₄, NBu₄OTf, NBu₄ OTs, PBu₄ Cl, or PBu₄ Br as the stabilizer proceed in much thesame way.

EXAMPLE 55

The procedure and processing are analogous to that of Example 31.Electrolyte: 100 ml of 0.05M tetrabutylammonium bromide in acetonitrile.Metal salt: 0.5 g of Pd(OAc)₂. Charge passed: 430 C. Product: 367 mg ofa black powder. This powder very readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 57% of palladium. Yield: 89%. Diameter: 1-5 nm.Electrolyses with NBu₄ Cl, NBu₄ I, NBu₄ ClO₄, NBu₄ PF₆, NBu₄ BF₄, NBu₄OTf, NBu₄ OTs, PBu₄ Cl, or PBu₄ Br as the stabilizer proceed in much thesame way.

EXAMPLE 56

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Current: 1 mA. Product: 630 mg of a grey-black powder. Thispowder readily dissolves in DMF, and is insoluble in water, diethylether, THF, acetonitrile, toluene, and pentane.

Elemental analysis: 52% of platinum. Yield: 90%. Diameter: 6-15 nm. Ascompared to Example 31 and Example 57, electrolysis with low currentdensities results in larger colloids.

EXAMPLE 57

The procedure and processing are analogous to that of Example 31.Current: 195 mA. Product: 788 mg of a grey-black powder. This powderreadily dissolves in DMF, and is insoluble in water, diethyl ether, THF,acetonitrile, toluene, and pentane.

Elemental analysis: 38% of platinum. Yield: 82%. Diameter: <2 nm. Ascompared to Example 31 and Example 56, electrolysis with high currentdensities results in smaller colloids.

    ______________________________________                                        Example                                                                              current density [mA/cm.sup.2 ]                                                                  colloid diameter [nm]                                ______________________________________                                        56     0.6                6-15                                                31     10.00             3-5                                                  57     65.00             <2                                                   ______________________________________                                    

EXAMPLE 58

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 100 ml of 0.1M tetrabutylammonium acetate in THF. 3.5 g of driedand mortar-ground alumina is suspended in this solution as a substratematerial. Two sheets of pure platinum (4×4 cm² geometric electrodesurface area, thickness 0.5 mm) at a distance of about 3 mm are used asthe electrodes. All operations must be performed under an inert gasatmosphere (argon or nitrogen). With stirring, 0.5 g of RuCl₃ •H₂ O isdissolved in the electrolyte and a current of 5 mA which is increased to30 mA in the course of 10 minutes is passed between the platinumelectrodes. By means of jacket cooling, the electrolytic cell ismaintained at 18° C. In the course of the electrolysis, the electrolyteturns deep-black. After a charge of 635 C has been passed, theelectrolysis is stopped. After 2 hours, the supernatant is pressed offunder inert gas and the residual solid is washed twice with 20 ml ofdiethyl ether. Drying under oil pump vacuum for 24 hours yields 3.8 g ofa light-grey powder.

Elemental analysis: 3.9% of ruthenium. This corresponds to an efficiencyof 68% with an uptake of 3 electrons per ruthenium ion. Transmissionelectron micrographs show a narrow size distribution of colloids whichare all <5 nm in diameter and have spherical geometries. Electrolyseswith active charcoal, SiO₂, TiO₂, La₂ O₃, Y₂ O₃, MgO, or Kevlar® as thesubstrate material proceed in much the same way.

EXAMPLE 59

In a 150 ml nitrogenized vessel, 250 mg of palladium colloid (cf.Example 52, metal content 26%, average size 3-5 nm) is dissolved in 100ml of oxygen-free water. All operations must be performed under an inertgas atmosphere (argon or nitrogen). With vigorous stirring, 5.0 g ofdried and mortar-ground titaniumdioxide is added and stirring iscontinued for another 50 min. After 2 hours, the solvent is evaporatedunder oil pump vacuum. Drying under oil pump vacuum for 24 hours yields5.25 g of a light-grey powder.

Elemental analysis: 1.3% of palladium. Transmission electron micrographsshow a narrow size distribution of colloids which are all 3-5 nm indiameter, have spherical geometries and are individually fixed on thesubstrate. Thus, the same size distribution as prior to substratefixation is observed. Substrate fixations using active charcoal, Al₂ O₃,SiO₂, La₂ O₃, Y₂ O₃, MgO, or Kevlar® as the substrate material proceedin much the same way.

EXAMPLE 60

In a 50 ml nitrogenized vessel, 100 mg of palladium colloid (cf. Example44, metal content 72%, average size 1-5 nm) is dissolved in 10 ml ofTHF. All operations must be performed under an inert gas atmosphere(argon or nitrogen). With the use of ultrasonic waves, a solution of 0.5g of dried poly(p-phenylene-vinylene) in 10 ml of THF is added. After 10min, the solvent is evaporated under oil pump vacuum. Drying under oilpump vacuum for two hours yields 600 mg of a dark powder.

Elemental analysis: 12% of palladium. The powder thus prepared is veryuseful for the preparation of films and workpieces. Embeddings usingPMMA and polystyrene proceed in much the same way.

EXAMPLE 61

The procedure and processing are analogous to that of Example 31. Metalsalts: 0.25 g of PtCl₂ and 0.25 g of RhCl₃ •3H₂ O. Charge passed: 530 C.Product: 360 mg of a grey-black powder. This powder readily dissolves inDMF, and is insoluble in water, diethyl ether, THF, acetonitrile,toluene, and pentane.

Elemental analysis: 42% of platinum and 24% of rhodium. Yield: 86%.Diameter: <3 nm. Energy-dispersive X-ray spot analysis (EDX) ofindividual particles clearly shows that both platinum and rhodium arepresent in the colloids. Comparative TEM/STM investigations of thesecolloids (adsorbed from a DMF solution, substrate: 200 nm gold on Tempaxquartz carrier) clearly show coating of the metal cores with amonomolecular layer of stabilizer. Electrolyses of platinum from PtBr₂,PtI₂, platinum(II) acetylacetonate, and of rhodium from RhCl₃ and RhBr₃•xH₂ O proceed in much the same way.

EXAMPLE 62

The procedure and processing are analogous to that of Example 31. Metalsalts: 450 mg of PtCl₂ and 50 mg of RhCl₃ •3H₂ O. Charge passed: 400 C.Product: 340 mg of a grey-black powder. This powder readily dissolves inDMF, and is insoluble in water, diethyl ether, THF, acetonitrile,toluene, and pentane.

Elemental analysis: 62% of platinum and 4% of rhodium. Yield: 83%.Diameter: <3 nm. Energy-dispersive X-ray spot analysis (EDX) ofindividual particles clearly shows that both platinum and rhodium arepresent in the colloids. Electrolyses of platinum from PtBr₂, PtI₂,platinum(II) acetylacetonate, and of rhodium from RhCl₃ and RhBr₃ •xH₂ Oproceed in much the same way.

EXAMPLE 63

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 100 ml of 0.1M tetraoctylammonium bromide in THF. The followingserve as electrodes: a sheet of pure platinum is used as the cathode anda sheet of pure copper is used as the anode (1.5×2 cm² geometricelectrode surface area, thickness 0.5 mm) at a distance of about 3 mm.All operations must be performed under an inert gas atmosphere (argon ornitrogen). Under ultrasonic action, 0.5 g of PdBr₂ is dissolved in theelectrolyte and a current of 2 mA which is increased to 20 mA in thecourse of 10 minutes is passed between the electrodes. By means ofjacket cooling, the electrolytic cell is maintained at 20° C. In thecourse of the electrolysis, the electrolyte turns deep-black. After acharge of 490 C has been passed, the electrolysis is stopped and theelectrolyte is pressed into a 200 ml nitrogenized vessel. Addition of 15ml of oxygen-free water to the electrolyte results in the formation of agrey-black precipitate upon vigorous shaking. After 24 hours, theslightly brown clear supernatant is pressed off under inert gas and theprecipitate is washed twice with 10 ml of diethyl ether. Drying underoil pump vacuum for 24 hours yields 570 mg of a black powder. Thispowder readily dissolves in THF and toluene, and is insoluble in water,diethyl ether, DMF, acetonitrile, and pentane.

Elemental analysis: 35% of palladium and 15% of copper. The remainder isthe tetraoctylammonium bromide stabilizer. This corresponds to anefficiency of 97%. Transmission electron micrographs show a sizedistribution of colloids which are all 1-5 nm in diameter and havespherical geometries. Energydispersive X-ray spot analysis (EDX) ofindividual particles clearly shows that both palladium and copper arepresent in the colloids. Electrolyses with Noct₄ Cl, Noct₄ ClO₄, Noct₄PF₆, Noct₄ BF₄, Noct₄ OTf, Noct₄ OTs, Poct₄ Cl, or Poct₄ Br as thestabilizer proceed in much the same way.

EXAMPLE 64

The procedure and processing are analogous to that of Example 63. Metalsalt: 0.5 g of PtCl₂. Charge passed: 495 C. Product: 675 mg of a blackpowder. This powder readily dissolves in THF and toluene, and isinsoluble in water, diethyl ether, DMF, acetonitrile, and pentane.

Elemental analysis: 53% of platinum and 23% of copper. Yield: 98%.Diameter: 1-5 nm. Energy-dispersive X-ray spot analysis (EDX) ofindividual particles clearly shows that both platinum and copper arepresent in the colloids. Electrolyses with Noct₄ Cl, Noct₄ ClO₄, Noct₄PF₆, Noct₄ BF₄, Noct₄ OTf, Noct₄ OTs, Poct₄ Cl, or Poct₄ Br as thestabilizer proceed in much the same way.

EXAMPLE 65

The procedure and processing are analogous to that of Example 63.Electrolyte: 100 ml of 0.1M tetrabutylammonium bromide in THF. Aselectrodes, a sheet of pure platinum is used as the cathode and a tinsheet is used as the anode (1.5×2 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm. Metal salt: 0.5 g ofPtCl₂. Charge passed: 800 C. Product: 745 mg of a black powder. Thispowder readily dissolves in DMF, and is insoluble in water, THF,toluene, diethyl ether, acetonitrile, and pentane.

Elemental analysis: 49% of platinum and 36% of tin. Yield: 98%.Diameter: 3-5 nm. Energy-dispersive X-ray spot analysis (EDX) ofindividual particles clearly shows that both platinum and tin arepresent in the colloids. Comparative TEM/STM investigations of thesecolloids (adsorbed from a DMF solution, substrate: 200 nm gold on Tempaxquartz carrier) clearly show coating of the metal cores with amonomolecular layer of stabilizer. Electrolyses with NBu₄ Cl, NBu₄ I,NBu₄ ClO₄, NBu₄ PF₆, NBu₄ BF₄, NBu₄ OTf, NBu₄ OTs, PBu₄ Cl, or PBu₄ Bras the stabilizer proceed in much the same way.

EXAMPLE 66

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte arecharged 90 ml of 0.1M tetrabutylammonium acetate in THF/water (10/1).5.0 g of mortar-ground active charcoal is suspended in this solution asa substrate material. Two sheets of pure platinum (1.5×2 cm² geometricelectrode surface area, thickness 0.5 mm) at a distance of about 3 mmare used as the electrodes. All operations must be performed under aninert gas atmosphere (argon or nitrogen). Under ultrasonic action, 0.25g of PtCl₂ and 0.25 g of RhCl₃ •3H₂ O is dissolved in the electrolyteand a current of 5 mA which is increased to 30 mA in the course of 10minutes is passed between the platinum electrodes. By means of jacketcooling, the electrolytic cell is maintained at 20° C. In the course ofthe electrolysis, the electrolyte turns deep-black. After a charge of530 C has been passed, the electrolysis is stopped and the electrolyteis pressed into a 200 ml nitrogenized vessel. The slightly brown clearsupernatant is pressed off under inert gas and the residual solid iswashed twice with 10 ml of diethyl ether. Drying under oil pump vacuumfor one hour yields 5.36 g of a black powder.

Elemental analysis: 3.1% of platinum and 1.7% of rhodium. Thiscorresponds to an efficiency of 83% with an uptake of 2 electrons perplatinum ion and 3 electrons per rhodium ion. Transmission electronmicrographs show a narrow size distribution of colloids which are all <3nm in diameter, have spherical geometries and are individually fixed onthe substrate. Energy-dispersive X-ray spot analysis (EDX) of individualparticles clearly shows that both platinum and rhodium are present inthe colloids. Electrolyses of platinum from PtBr₂, PtI₂, platinum(II)acetylacetonate, and of rhodium from RhCl₃ and RhBr₃ •xH₂ O proceed inmuch the same way.

EXAMPLE 67

In a miniautoclave, 85 mg of palladium on active charcoal (similar toExample 59, metal content 5%) are suspended in 20 ml of DMF. After 2mmol of bromobenzene, 2 mmol of styrene, and 4 mmol oftetrabutylammonium acetate have been added, heating at 120° C. isperformed with shaking. After 16 h, 267 mg of stilbene can be isolatedfrom the reaction solution. This corresponds to a 74% conversion.

EXAMPLE 68

In a miniautoclave, 25 mg of rhodium colloid (similar to Example 45,metal content 38%) are dissolved in 20 ml of THF. After 5 mmol ofcyclohexene has been added, the vessel is exposed to an atmosphere ofhydrogen (1 bar) with shaking at 20° C. After 1 h, hydration iscomplete, and in the gas chromatogram of the reaction solution,cyclohexane and THF can be solely detected. This corresponds to a 100%conversion.

EXAMPLE 69

In an autoclave, 150 mg of ruthenium/alumina catalyst (similar toExample 58, metal content 3.9%) is suspended in 25 ml of benzene and 5ml of water. Then, the suspension is heated at 145° C. and pressurizedwith hydrogen (total pressure 50 bar) with stirring. After 25 min, thegas chromatogram shows a product distribution of 31% of cyclohexene and69% of cyclohexane.

EXAMPLE 70

In a multi-purpose electrolytic cell for 20-100 ml of electrolyte, 10 mgof palladium colloid (cf. Example 32, metal content 62%) is dissolved in20 ml of DMF. As electrodes, a sheet of pure platinum is used as thecathode and a piece of freshly drawn graphite (HOPG) is used as theanode (1×1 cm² geometric electrode surface area) at a distance of about6 mm. All operations must be performed under an inert gas atmosphere(argon or nitrogen). For 30 seconds, a voltage of 30 volts is appliedbetween the electrodes. Subsequently, the graphite electrode is removedand washed twice with 3 ml of diethyl ether.

Scanning force microscopic studies clearly show covering of the surfacewith the colloid.

EXAMPLE 71

In a 2 ml plastic vessel, 160 μl of 0.1M aqueous sodium fluoride isadded with stirring to 4 mmol of Mg(OEt)₂, 1 mmol ofmethyltrimethoxysilane, 1 mg of palladium colloid (metal content 44%),and 200 μl of THF. After drying at 50° C. for 24 hours, remainingvolatile components are removed under oil pump vacuum for another 24hours. Then, the mortar-ground residue in ethanol is refluxed for 24hours. After decantation, the solid is dried under oil pump vacuum.

Elemental analysis: 0.1% of palladium.

EXAMPLE 72

In a 60 ml miniautoclave, 85 mg of palladium in sol-gel matrix (cf.Example 71, metal content 0.1%) are suspended in 20 ml of DMF. After 2mmol of iodobenzene, 2 mmol of styrene, and 4 mmol of tetrabutylammoniumacetate have been added, heating at 60° C. is performed with shaking.After 12 h, 288 mg of stilbene can be isolated from the reactionsolution. This corresponds to an 80% yield.

EXAMPLE 73

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of YCl₃. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 750 C. Within24 hours, a grey-black precipitate forms. Product: 420 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in diethyl ether, THF, acetonitrile, toluene, and pentane.

Elemental analysis: 22% of yttrium. Yield: 40%. Diameter: <5 nm.

EXAMPLE 74

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of ZrCl₄. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 825 C. Within24 hours, a grey-black precipitate forms. Product: 244 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in diethyl ether, THF, acetonitrile, toluene, and pentane.

Elemental analysis: 36% of zirconium. Yield: 45%. Diameter: <3nm.

EXAMPLE 75

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of NbBr₅. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 500 C. Within24 hours, a grey-black precipitate forms. Product: 114 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 50% of niobium. Yield: 60%. Diameter: 1-3 nm.

EXAMPLE 76

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of ReCl₃. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 500 C. Within24 hours, a grey-black precipitate forms. Product: 423 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 55% of rhenium. Yield: 73%. Diameter: <5 nm.

EXAMPLE 77

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of YbCl₃. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 550 C. Within24 hours, a grey-black precipitate forms. Product: 400 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in diethyl ether, THF, acetonitrile, toluene, and pentane.

Elemental analysis: 24% of ytterbium. Yield: 31%. Diameter: <5 nm.

EXAMPLE 78

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of UBr₃. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 300 C. Within24 hours, a grey-black precipitate forms. Product: 425 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 36% of uranium. Yield: 61%. Diameter: <3 nm.

EXAMPLE 79

The procedure and processing are analogous to that of Example 31. Twosheets of pure platinum (4×4 cm² geometric electrode surface area,thickness 0.5 mm) at a distance of about 3 mm are used as theelectrodes. Metal salt: 0.5 g of CdBr₂. By means of jacket cooling, theelectrolytic cell is maintained at 18° C. Charge passed: 350 C. Within24 hours, a grey-black precipitate forms. Product: 260 mg of agrey-black powder. This powder readily dissolves in DMF, and isinsoluble in water, diethyl ether, THF, acetonitrile, toluene, andpentane.

Elemental analysis: 72% of cadmium. Yield: 91%. Diameter: 2-10 nm.

EXAMPLE 80

The procedure and processing are analogous to that of Example 31. Metalsalt: 0.5 g of Bi(OAc)₃. Charge passed: 400 C. Product: 223 mg of ablack powder. This powder readily dissolves in DMF, and is insoluble inwater, THF, diethyl ether, toluene, acetonitrile, and pentane.

Elemental analysis: 68% of bismuth. Yield: 56%. Diameter: 5-10 nm.

EXAMPLE 81

The procedure and processings are analogous to that of Example 31.Electrolyte 100 ml of 0.1M 3-(dimethyldodecylammonio)propanesulfonate inwater. Metal salt: 0.5 g Pd(OAc)₂. Current 10 mA, increased to 50 mA inthe course of 10 minutes. Charge passed: 430 C. The solvent isevaporated under oil pump vacuum and the residue is washed twice with amixture of thanol/ether (1:10). Drying under oil pump vacuum for 24hours yields 548 mg of a light-grey powder.

Elemental analysis: 39% palladium. Transmission electron micrographsshow a narrow size distribution of colloids which are all <10 nm indiameter.

EXAMPLE 82

The procedure and processings are analogous to that of Example 81. Metalsalt: 0.5 g PtCl₂. Charge passed: 365 C. The solvent is evaporated underoil pump vacuum and the residue is washed twice with a mixture ofethanol/ether (1:10). Drying under oil pump vacuum for 24 hours yields720 mg of a light-grey powder.

Elemental analysis: 46% platinum. Transmission electron micrographs showa narrow size distribution of colloids which are all <10 nm diameter.

EXAMPLE 83

In a 150 ml vessel, 100 mg of palladium colloid (cf. Example 52, metalcontent 57%, average size 3-5 nm) is dissolved in 100 ml of water. Withvigorous stirring 5.0 g mortar ground alumina is added and stirring iscontinued for another 3 hours. After 30 min th colorless supernatant issyphoned off. Drying under oil pump vacuum for 24 hours yields 5.1 g ofa light-grey powder.

Elemental analysis: 1.1% palladium. Transmission electron mircrographsshow a narrow size distribution of colloids which are all 3-5 nm indiameter, have spherical geometries and are individually fixed on thesubstrate. These supported palladium clusters are embedded in carbon bymeans of glow evaporation. Ultramicrotome sections of this material showthat the metal colloid is only on the surface of the alumina grains.

EXAMPLE 84

In a 150 ml vessel, 150 mg of palladium colloid (cf. Example 52, metalcontent 57%, average size 3-5 nm) is dissolved in 100 ml of water. Withvigorous stirring 3.0 g mortar ground carbon black (Vulcan® XC-72) isadded and stirring is continued for another 3 hours. After 30 min thecolorless supernatant is syphoned off. Drying under oil pump vacuum for24 hours yields 3.15 g of a black powder.

Elemental analysis: 2.7% palladium. Transmission electron micrographsshow a narrow size distribution of colloids which are all 3-5 nm indiameter, have spherical geometries and are individually fixed on thesubstrate. Thus, the same size distribution as prior to substratefixation is observed. Substrate fixations using Al₂ O₃, TiO₂, SiO₂, La₂O₃, Y₂ O₃, MgO or Kevlar® as the substrate material proceed in much thesame way.

EXAMPLE 85

In a 50 ml vessel, 15 mg of palladium colloid (cf. Example 52, metalcontent 57%, average size 3-5 nm) is dissolved in 100 ml of water. With,vigorous shaking 250 mg Bioran® controlled pore glas (pore diameter 101nm, particle size 130-250 μm) is added and shaking is continued foranother 3 hours. After 30 min the colorless supernatant is filtered off.Drying of the residue under oil pump vacuum for 24 hours yields 264 mgof a grey material.

Elemental analysis: 3.2% palladium. Transmission electron mircrographsshow a narrow size distribution of colloids which are all 3-5 nm indiameter, have spherical geometries and are individually fixed on thesubstrate. Thus, the same size distribution as prior to substratefixation is observed. Substrate fixations using Siran® as the substratematerial proceed in much the same way.

We claim:
 1. A method for the electrochemical preparation of a metalcolloid of a particle size of 0.5 to 50 nm, which comprises cathodicallyreducing in an orfianic solvent optionally containing water at -78° C.to +120° C. at least one salt of at least one metal of groups Ib, IIb,III, IV, V, VI, VIIb, VIII, lanthanoides, or actinoides of the periodictable, there being present in the solvent a stabilizer comprising atleast one quaternary ammonium salt of the formula

    R.sup.1 R.sup.2 R.sup.3 R.sup.4 N.sup.+ X.sup.-

or quaternary phosphonium salt of the formula

    R.sup.1 R.sup.2 R.sup.3 R.sup.4 P.sup.+ X.sup.-

in which R¹ R² R³ and R⁴ each independently is at least one memberselected from the group consisting of C₁₋₁₈ alkyl, C₁₋₁₈ alkyl-phenyl,and aryl, and X is at least one member selected from the groupconsisting of Cl, Br, I, PF₆, R¹ COO-- and R¹ SO₃.
 2. The methodaccording to claim 1, wherein during the reduction there is present inthe solvent at least one quaternary ammonium salt of the formula

    R.sup.1 R.sup.2 R.sup.3 R.sup.4 N.sup.+ X.sup.-.


3. The method according to claim 2, wherein the quaternary ammonium saltis chiral or has a chiral center in its ligand.
 4. The method accordingto claim 1, wherein the metal comprises at least one of Fe, Co, Ni, Pd,Pt, Ir, Rh, Cu, Ag and Au.
 5. The method according to claim 1, wherein Xis at least one of Cl, Br and I.
 6. The method according to claim 1,wherein the solvent comprises at least one of tetrahydrofuran, tolueneand acetonitrile.
 7. The method according to claim 1, wherein thereduction is effected at room temperature.
 8. The method according toclaim 1, wherein the current density is maintained between 0.1 mA/cm²and 40 mA/cm² to obtain a particle size of 0.5 to 15 nm.
 9. The methodaccording to claim 1, wherein the reduction is effected in anelectrolytic cell comprising the solvent, one inert electrode, and atleast one electrode comprising the metal to be reduced, and at least onesalt of the metal.
 10. The method according to claim 1, wherein duringthe reduction there is present in the solvent at least one inertsubstrate selected from the group consisting of carbon black, activecharcoal, glass, an inorganic oxide and an organic polymer, thesubstrate on its surface adsorbing the metal colloid as formed.
 11. Themethod according to claim 10, further comprising the step of removingthe solvent.
 12. The method according to claim 1, wherein the organicsolvent and contents after reduction is contacted with at least oneinert substrate selected from the group consisting of carbon black,active charcoal, glass, an inorganic oxide and an organic polymer, thesubstrate on its surface adsorbing the metal colloid.
 13. The methodaccording to claim 12, wherein during the reduction there is present inthe organic solvent at least one inert substrate selected from the groupconsisting of carbon black, active charcoal, glass, an inorganic oxideand an organic polymer, the substrate on its surface adsorbing the metalcolloid as formed.
 14. The method according to claim 1, furthercomprising the step of hydrolyzing or polymerizing by the sol-gelprocess at least one tetraalkoxysilane, alkyltrialkoxysilane ormagnesium alkoxylate whereby the metal colloid is incorporated into theproduct of the hydrolysis or polymerization.
 15. The method according toclaim 1, further comprising the step of polymerizing a monomer,resulting in the metal colloid being incorporated into the resultingpolymer.
 16. The method according to claim 1, wherein a supportingelectrolyte is also present in the organic solvent during the reduction.17. A method according to claim 1, wherein at least one metal salt ofthe metal being reduced is also present in the organic solvent duringthe reduction.